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Misuse, problem use, abuse, and heavy use of alcohol refer to improper use of alcohol, which may cause physical, social, or moral harm to the drinker. The Dietary Guidelines for Americans, issued by the United States Department of Agriculture (USDA) in 2005, defines "moderate use" as no more than two alcoholic beverages a day for men and no more than one alcoholic beverage a day for women. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines binge drinking as the amount of alcohol leading to a blood alcohol content (BAC) of 0.08, which, for most adults, would be reached by consuming five drinks for men or four for women over a two-hour period. According to the NIAAA, men may be at risk for alcohol-related problems if their alcohol consumption exceeds 14 standard drinks per week or 4 drinks per day, and women may be at risk if they have more than 7 standard drinks per week or 3 drinks per day. It defines a standard drink as one 12-ounce bottle of beer, one 5-ounce glass of wine, or 1.5 ounces of distilled spirits. Despite this risk, a 2014 report in the National Survey on Drug Use and Health found that only 10% of either "heavy drinkers" or "binge drinkers" defined according to the above criteria also met the criteria for alcohol dependence, while only 1.3% of non-binge drinkers met the criteria. An inference drawn from this study is that evidence-based policy strategies and clinical preventive services may effectively reduce binge drinking without requiring addiction treatment in most cases.
Alcoholism
The term alcoholism is commonly used amongst laypeople, but the word is poorly defined. Despite the imprecision inherent in the term, there have been attempts to define how the word alcoholism should be interpreted when encountered. In 1992, it was defined by the National Council on Alcoholism and Drug Dependence (NCADD) and ASAM as "a primary, chronic disease characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking." MeSH has had an entry for alcoholism since 1999, and references the 1992 definition.
The WHO calls alcoholism "a term of long-standing use and variable meaning", and use of the term was disfavored by a 1979 WHO expert committee. | Alcoholism | Wikipedia | 489 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
In professional and research contexts, the term alcoholism is not currently favored, but rather alcohol abuse, alcohol dependence, or alcohol use disorder are used. Talbot (1989) observes that alcoholism in the classical disease model follows a progressive course: if people continue to drink, their condition will worsen. This will lead to harmful consequences in their lives, physically, mentally, emotionally, and socially. Johnson (1980) proposed that the emotional progression of the addicted people's response to alcohol has four phases. The first two are considered "normal" drinking and the last two are viewed as "typical" alcoholic drinking. Johnson's four phases consist of:
Learning the mood swing. People are introduced to alcohol (in some cultures this can happen at a relatively young age), and they enjoy the happy feeling it produces. At this stage, there is no emotional cost.
Seeking the mood swing. People will drink to regain that happy feeling in phase 1; the drinking will increase as more alcohol is required to achieve the same effect. Again at this stage, there are no significant consequences.
At the third stage there are physical and social consequences such as hangovers, family problems, and work problems. People will continue to drink excessively, disregarding the problems.
The fourth stage can be detrimental with a risk for premature death. People in this phase now drink to feel normal and block out the feelings of overwhelming guilt, remorse, anxiety, and shame they experience when sober.
DSM and ICD
In the United States, the Diagnostic and Statistical Manual of Mental Disorders (DSM) is the most common diagnostic guide for substance use disorders, whereas most countries use the International Classification of Diseases (ICD) for diagnostic (and other) purposes. The two manuals use similar but not identical nomenclature to classify alcohol problems.
Social barriers
Attitudes and social stereotypes can create barriers to the detection and treatment of alcohol use disorder. This is more of a barrier for women than men. Fear of stigmatization may lead women to deny that they have a medical condition, to hide their drinking, and to drink alone. This pattern, in turn, leads family, physicians, and others to be less likely to suspect that a woman they know has alcohol use disorder. In contrast, reduced fear of stigma may lead men to admit that they are having a medical condition, to display their drinking publicly, and to drink in groups. This pattern, in turn, leads family, physicians, and others to be more likely to suspect that a man they know is someone with an alcohol use disorder. | Alcoholism | Wikipedia | 511 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Screening
Screening is recommended among those over the age of 18. Several tools may be used to detect a loss of control of alcohol use. These tools are mostly self-reports in questionnaire form. Another common theme is a score or tally that sums up the general severity of alcohol use.
The CAGE questionnaire, named for its four questions, is one such example that may be used to screen patients quickly in a doctor's office.
The CAGE questionnaire has demonstrated a high effectiveness in detecting alcohol-related problems; however, it has limitations in people with less severe alcohol-related problems, white women and college students.
Other tests are sometimes used for the detection of alcohol dependence, such as the Alcohol Dependence Data Questionnaire, which is a more sensitive diagnostic test than the CAGE questionnaire. It helps distinguish a diagnosis of alcohol dependence from one of heavy alcohol use. The Michigan Alcohol Screening Test (MAST) is a screening tool for alcoholism widely used by courts to determine the appropriate sentencing for people convicted of alcohol-related offenses, driving under the influence being the most common. The Alcohol Use Disorders Identification Test (AUDIT), a screening questionnaire developed by the World Health Organization, is unique in that it has been validated in six countries and is used internationally. Like the CAGE questionnaire, it uses a simple set of questions – a high score earning a deeper investigation. The Paddington Alcohol Test (PAT) was designed to screen for alcohol-related problems amongst those attending Accident and Emergency departments. It concords well with the AUDIT questionnaire but is administered in a fifth of the time.
Urine and blood tests
There are reliable tests for the actual use of alcohol, one common test being that of blood alcohol content (BAC). These tests do not differentiate people with alcohol use disorders from people without; however, long-term heavy drinking does have a few recognizable effects on the body, including:
Macrocytosis (enlarged MCV)
Elevated GGT
Moderate elevation of AST and ALT and an AST: ALT ratio of 2:1
High carbohydrate deficient transferrin (CDT)
With regard to alcoholism, BAC is useful to judge alcohol tolerance, which in turn is a sign of alcoholism. Electrolyte and acid-base abnormalities including hypokalemia, hypomagnesemia, hyponatremia, hyperuricemia, metabolic acidosis, and respiratory alkalosis are common in people with alcohol use disorders. | Alcoholism | Wikipedia | 496 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
However, none of these blood tests for biological markers is as sensitive as screening questionnaires.
Prevention
The World Health Organization, the European Union and other regional bodies, national governments and parliaments have formed alcohol policies in order to reduce the harm of alcoholism.
Increasing the age at which alcohol can be purchased, and banning or restricting alcohol beverage advertising are common methods to reduce alcohol use among adolescents and young adults in particular, see Alcoholism in adolescence. Another common method of alcoholism prevention is taxation of alcohol products – increasing price of alcohol by 10% is linked with reduction of consumption of up to 10%.
Credible, evidence-based educational campaigns in the mass media about the consequences of alcohol misuse have been recommended. Guidelines for parents to prevent alcohol misuse amongst adolescents, and for helping young people with mental health problems have also been suggested.
Because alcohol is often used for self-medication of conditions like anxiety temporarily, prevention of alcoholism may be attempted by reducing the severity or prevalence of stress and anxiety in individuals.
Management
Treatments are varied because there are multiple perspectives of alcoholism. Those who approach alcoholism as a medical condition or disease recommend differing treatments from, for instance, those who approach the condition as one of social choice. Most treatments focus on helping people discontinue their alcohol intake, followed up with life training and/or social support to help them resist a return to alcohol use. Since alcoholism involves multiple factors which encourage a person to continue drinking, they must all be addressed to successfully prevent a relapse. An example of this kind of treatment is detoxification followed by a combination of supportive therapy, attendance at self-help groups, and ongoing development of coping mechanisms. Much of the treatment community for alcoholism supports an abstinence-based zero tolerance approach popularized by the 12 step program of Alcoholics Anonymous; however, some prefer a harm-reduction approach.
Cessation of alcohol intake | Alcoholism | Wikipedia | 378 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Medical treatment for alcohol detoxification usually involves administration of a benzodiazepine, in order to ameliorate alcohol withdrawal syndrome's adverse impact. The addition of phenobarbital improves outcomes if benzodiazepine administration lacks the usual efficacy, and phenobarbital alone might be an effective treatment. Propofol also might enhance treatment for individuals showing limited therapeutic response to a benzodiazepine. Individuals who are only at risk of mild to moderate withdrawal symptoms can be treated as outpatients. Individuals at risk of a severe withdrawal syndrome as well as those who have significant or acute comorbid conditions can be treated as inpatients. Direct treatment can be followed by a treatment program for alcohol dependence or alcohol use disorder to attempt to reduce the risk of relapse. Experiences following alcohol withdrawal, such as depressed mood and anxiety, can take weeks or months to abate while other symptoms persist longer due to persisting neuroadaptations.
Psychological
Various forms of group therapy or psychotherapy are sometimes used to encourage and support abstinence from alcohol, or to reduce alcohol consumption to levels that are not associated with adverse outcomes. Mutual-aid group-counseling is an approach used to facilitate relapse prevention. Alcoholics Anonymous was one of the earliest organizations formed to provide mutual peer support and non-professional counseling, however the effectiveness of Alcoholics Anonymous is disputed. A 2020 Cochrane review concluded that Twelve-Step Facilitation (TSF) probably achieves outcomes such as fewer drinks per drinking day, however evidence for such a conclusion comes from low to moderate certainty evidence "so should be regarded with caution". Others include LifeRing Secular Recovery, SMART Recovery, Women for Sobriety, and Secular Organizations for Sobriety.
Manualized Twelve Step Facilitation (TSF) interventions (i.e. therapy which encourages active, long-term Alcoholics Anonymous participation) for Alcohol Use Disorder lead to higher abstinence rates, compared to other clinical interventions and to wait-list control groups.
Moderate drinking
Moderate drinking amongst people with alcohol dependence—often termed 'controlled drinking'—has been subject to significant controversy. Indeed, much of the skepticism toward the viability of moderate drinking goals stems from historical ideas about 'alcoholism', now replaced with 'alcohol use disorder' or alcohol dependence in most scientific contexts. A 2021 meta-analysis and systematic review of controlled drinking covering 22 studies concluded controlled drinking was a 'non-inferior' outcome to abstinence for many drinkers. | Alcoholism | Wikipedia | 511 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Rationing and moderation programs such as Moderation Management and DrinkWise do not mandate complete abstinence. While most people with alcohol use disorders are unable to limit their drinking in this way, some return to moderate drinking. A 2002 US study by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) showed that 17.7% of individuals diagnosed as alcohol dependent more than one year prior returned to low-risk drinking. This group, however, showed fewer initial symptoms of dependency.
A follow-up study, using the same subjects that were judged to be in remission in 2001–2002, examined the rates of return to problem drinking in 2004–2005. The study found abstinence from alcohol was the most stable form of remission for recovering alcoholics. There was also a 1973 study showing chronic alcoholics drinking moderately again, but a 1982 follow-up showed that 95% of subjects were not able to maintain drinking in moderation over the long term. Another study was a long-term (60 year) follow-up of two groups of alcoholic men which concluded that "return to controlled drinking rarely persisted for much more than a decade without relapse or evolution into abstinence." Internet based measures appear to be useful at least in the short term. | Alcoholism | Wikipedia | 258 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Medications
In the United States there are four approved medications for alcoholism: acamprosate, two methods of using naltrexone and disulfiram.
Acamprosate may stabilise the brain chemistry that is altered due to alcohol dependence via antagonising the actions of glutamate, a neurotransmitter which is hyperactive in the post-withdrawal phase. By reducing excessive NMDA activity which occurs at the onset of alcohol withdrawal, acamprosate can reduce or prevent alcohol withdrawal related neurotoxicity. Acamprosate reduces the risk of relapse amongst alcohol-dependent persons. Acamprosate is not recommended in those with advanced, decompensated liver cirrhosis due to the risk of liver toxicity.
Naltrexone is a competitive antagonist for opioid receptors, effectively blocking the effects of endorphins and opioids. Naltrexone may be given as a daily oral tablet or as a monthly intramuscular injection. Naltrexone is used to decrease cravings for alcohol and encourage abstinence. Alcohol causes the body to release endorphins, which in turn release dopamine and activate the reward pathways; hence in the body Naltrexone reduces the pleasurable effects from consuming alcohol. Evidence supports a reduced risk of relapse among alcohol-dependent persons and a decrease in excessive drinking. Naltrexone should not be used in those with advanced liver disease due to the risk of liver toxicity. Nalmefene also appears effective and works in a similar manner.
Disulfiram prevents the elimination of acetaldehyde by inhibiting the enzyme acetaldehyde dehydrogenase. Acetaldehyde is a chemical the body produces when breaking down ethanol. Acetaldehyde itself is the cause of many hangover symptoms from alcohol use. The overall effect is acute discomfort when alcohol is ingested characterized by flushing, nausea, a rapid heart rate and low blood pressure. Disulfiram should not be used in those with advanced liver disease due to the risk of life-threatening liver toxicity. | Alcoholism | Wikipedia | 438 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Several other drugs are also used and many are under investigation.
Benzodiazepines are a first line medication in the management of acute alcohol withdrawal, however their use outside of the acute withdrawal period is not recommended. Benzodiazepines with a shorter half life, such as lorazepam or oxazepam are preferred in the treatment of alcohol withdrawal as their shorter half lives and less active metabolites have a lower risk of confusion in those with liver disease. If used long-term, they can cause a worse outcome in alcoholism. Alcoholics on chronic benzodiazepines have a lower rate of achieving abstinence from alcohol than those not taking benzodiazepines. Initiating prescriptions of benzodiazepines or sedative-hypnotics in individuals in recovery has a high rate of relapse with one author reporting more than a quarter of people relapsed after being prescribed sedative-hypnotics. Those who are long-term users of benzodiazepines should not be withdrawn rapidly, as severe anxiety and panic may develop, which are known risk factors for alcohol use disorder relapse. Taper regimes of 6–12 months have been found to be the most successful, with reduced intensity of withdrawal.
Calcium carbimide works in the same way as disulfiram; it has an advantage in that the occasional adverse effects of disulfiram, hepatotoxicity and drowsiness, do not occur with calcium carbimide.
Ondansetron and topiramate are supported by tentative evidence in people with certain genetic patterns. Evidence for ondansetron is stronger in people who have recently started to abuse alcohol. Topiramate is a derivative of the naturally occurring sugar monosaccharide D-fructose. Review articles characterize topiramate as showing "encouraging", "promising", "efficacious", and "insufficient" results in the treatment of alcohol use disorders.
Evidence does not support the use of selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), antipsychotics, or gabapentin. | Alcoholism | Wikipedia | 454 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Research
Topiramate, a derivative of the naturally occurring sugar monosaccharide D-fructose, has been found effective in helping alcoholics quit or cut back on the amount they drink. Evidence suggests that topiramate antagonizes excitatory glutamate receptors, inhibits dopamine release, and enhances inhibitory gamma-aminobutyric acid function. A 2008 review of the effectiveness of topiramate concluded that the results of published trials are promising, however as of 2008, data was insufficient to support using topiramate in conjunction with brief weekly compliance counseling as a first-line agent for alcohol dependence. A 2010 review found that topiramate may be superior to existing alcohol pharmacotherapeutic options. Topiramate effectively reduces craving and alcohol withdrawal severity as well as improving quality-of-life-ratings.
Baclofen, a GABAB receptor agonist, is under study for the treatment of alcoholism. According to a 2017 Cochrane Systematic Review, there is insufficient evidence to determine the effectiveness or safety for the use of baclofen for withdrawal symptoms in alcoholism. Psilocybin-assisted psychotherapy is under study for the treatment of patients with alcohol use disorder. | Alcoholism | Wikipedia | 252 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Dual addictions and dependencies
Alcoholics may also require treatment for other psychotropic drug addictions and drug dependencies. The most common dual dependence syndrome with alcohol dependence is benzodiazepine dependence, with studies showing 10–20% of alcohol-dependent individuals had problems of dependence and/or misuse problems of benzodiazepine drugs such as diazepam or clonazepam. These drugs are, like alcohol, depressants. Benzodiazepines may be used legally, if they are prescribed by doctors for anxiety problems or other mood disorders, or they may be purchased as illegal drugs. Benzodiazepine use increases cravings for alcohol and the volume of alcohol consumed by problem drinkers. Benzodiazepine dependency requires careful reduction in dosage to avoid benzodiazepine withdrawal syndrome and other health consequences. Dependence on other sedative-hypnotics such as zolpidem and zopiclone as well as opiates and illegal drugs is common in alcoholics. Alcohol itself is a sedative-hypnotic and is cross-tolerant with other sedative-hypnotics such as barbiturates, benzodiazepines and nonbenzodiazepines. Dependence upon and withdrawal from sedative-hypnotics can be medically severe and, as with alcohol withdrawal, there is a risk of psychosis or seizures if not properly managed.
Epidemiology
The World Health Organization estimates that there are about 380 million people with alcoholism worldwide (5.1% of the population over 15 years of age), with it being most common among males and young adults. Geographically, it is least common in Africa (1.1% of the population) and has the highest rates in Eastern Europe (11%).
in the United States, about 17 million (7%) of adults and 0.7 million (2.8%) of those age 12 to 17 years of age are affected. About 12% of American adults have had an alcohol dependence problem at some time in their life. | Alcoholism | Wikipedia | 423 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
In the United States and Western Europe, 10–20% of men and 5–10% of women at some point in their lives will meet criteria for alcoholism. In England, the number of "dependent drinkers" was calculated as over 600,000 in 2019. Estonia had the highest death rate from alcohol in Europe in 2015 at 8.8 per 100,000 population. In the United States, 30% of people admitted to hospital have a problem related to alcohol.
Within the medical and scientific communities, there is a broad consensus regarding alcoholism as a disease state. For example, the American Medical Association considers alcohol a drug and states that "drug addiction is a chronic, relapsing brain disease characterized by compulsive drug seeking and use despite often devastating consequences. It results from a complex interplay of biological vulnerability, environmental exposure, and developmental factors (e.g., stage of brain maturity)." Alcoholism has a higher prevalence among men, though, in recent decades, the proportion of female alcoholics has increased. Current evidence indicates that in both men and women, alcoholism is 50–60% genetically determined, leaving 40–50% for environmental influences. Most alcoholics develop alcoholism during adolescence or young adulthood.
Prognosis
Alcoholism often reduces a person's life expectancy by around ten years. The most common cause of death in alcoholics is from cardiovascular complications. There is a high rate of suicide in chronic alcoholics, which increases the longer a person drinks. Approximately 3–15% of alcoholics die by suicide, and research has found that over 50% of all suicides are associated with alcohol or drug dependence. This is believed to be due to alcohol causing physiological distortion of brain chemistry, as well as social isolation. Suicide is also common in adolescent alcohol abusers. Research in 2000 found that 25% of suicides in adolescents were related to alcohol abuse. | Alcoholism | Wikipedia | 381 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Among those with alcohol dependence after one year, some met the criteria for low-risk drinking, even though only 26% of the group received any treatment, with the breakdown as follows: 25% were found to be still dependent, 27% were in partial remission (some symptoms persist), 12% asymptomatic drinkers (consumption increases chances of relapse) and 36% were fully recovered – made up of 18% low-risk drinkers plus 18% abstainers. In contrast, however, the results of a long-term (60-year) follow-up of two groups of alcoholic men indicated that "return to controlled drinking rarely persisted for much more than a decade without relapse or evolution into abstinence....return-to-controlled drinking, as reported in short-term studies, is often a mirage."
History
Historically the name dipsomania was coined by German physician C. W. Hufeland in 1819 before it was superseded by alcoholism. That term now has a more specific meaning. The term alcoholism was first used by Swedish physician Magnus Huss in an 1852 publication to describe the systemic adverse effects of alcohol.
Alcohol has a long history of use and misuse throughout recorded history. Biblical, Egyptian and Babylonian sources record the history of abuse and dependence on alcohol. In some ancient cultures alcohol was worshiped and in others, its misuse was condemned. Excessive alcohol misuse and drunkenness were recognized as causing social problems even thousands of years ago. However, the defining of habitual drunkenness as it was then known as and its adverse consequences were not well established medically until the 18th century. In 1647 a Greek monk named Agapios was the first to document that chronic alcohol misuse was associated with toxicity to the nervous system and body which resulted in a range of medical disorders such as seizures, paralysis, and internal bleeding. In the 1910s and 1920s, the effects of alcohol misuse and chronic drunkenness boosted membership of the temperance movement and led to the prohibition of alcohol in many countries in North America and the Nordic countries, nationwide bans on the production, importation, transportation, and sale of alcoholic beverages that generally remained in place until the late 1920s or early 1930s; these policies resulted in the decline of death rates from cirrhosis and alcoholism. In 2005, alcohol dependence and misuse was estimated to cost the US economy approximately 220 billion dollars per year, more than cancer and obesity.
Society and culture | Alcoholism | Wikipedia | 501 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
The various health problems associated with long-term alcohol consumption are generally perceived as detrimental to society; for example, money due to lost labor-hours, medical costs due to injuries due to drunkenness and organ damage from long-term use, and secondary treatment costs, such as the costs of rehabilitation facilities and detoxification centers. Alcohol use is a major contributing factor for head injuries, motor vehicle injuries (27%), interpersonal violence (18%), suicides (18%), and epilepsy (13%). Beyond the financial costs that alcohol consumption imposes, there are also significant social costs to both the alcoholic and their family and friends. For instance, alcohol consumption by a pregnant woman can lead to an incurable and damaging condition known as fetal alcohol syndrome, which often results in cognitive deficits, mental health problems, an inability to live independently and an increased risk of criminal behaviour, all of which can cause emotional stress for parents and caregivers. Estimates of the economic costs of alcohol misuse, collected by the World Health Organization, vary from 1–6% of a country's GDP. One Australian estimate pegged alcohol's social costs at 24% of all drug misuse costs; a similar Canadian study concluded alcohol's share was 41%. One study quantified the cost to the UK of all forms of alcohol misuse in 2001 as £18.5–20 billion. All economic costs in the United States in 2006 have been estimated at $223.5 billion.
The idea of hitting rock bottom refers to an experience of stress that can be attributed to alcohol misuse. There is no single definition for this idea, and people may identify their own lowest points in terms of lost jobs, lost relationships, health problems, legal problems, or other consequences of alcohol misuse. The concept is promoted by 12-step recovery groups and researchers using the transtheoretical model of motivation for behavior change. The first use of this slang phrase in the formal medical literature appeared in a 1965 review in the British Medical Journal, which said that some men refused treatment until they "hit rock bottom", but that treatment was generally more successful for "the alcohol addict who has friends and family to support him" than for impoverished and homeless addicts. | Alcoholism | Wikipedia | 461 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
Stereotypes of alcoholics are often found in fiction and popular culture. The "town drunk" is a stock character in Western popular culture. Stereotypes of drunkenness may be based on racism or xenophobia, as in the fictional depiction of the Irish as heavy drinkers. Studies by social psychologists Stivers and Greeley attempt to document the perceived prevalence of high alcohol consumption amongst the Irish in America. Alcohol consumption is relatively similar between many European cultures, the United States, and Australia. In Asian countries that have a high gross domestic product, there is heightened drinking compared to other Asian countries, but it is nowhere near as high as it is in other countries like the United States. It is also inversely seen, with countries that have very low gross domestic product showing high alcohol consumption. In a study done on Korean immigrants in Canada, they reported alcohol was typically an integral part of their meal but is the only time solo drinking should occur. They also generally believe alcohol is necessary at any social event, as it helps conversations start.
Peyote, a psychoactive agent, has even shown promise in treating alcoholism. Alcohol had actually replaced peyote as Native Americans' psychoactive agent of choice in rituals when peyote was outlawed. | Alcoholism | Wikipedia | 249 | 2965 | https://en.wikipedia.org/wiki/Alcoholism | Biology and health sciences | Drugs and medication | null |
In mathematics, an abelian group, also called a commutative group, is a group in which the result of applying the group operation to two group elements does not depend on the order in which they are written. That is, the group operation is commutative. With addition as an operation, the integers and the real numbers form abelian groups, and the concept of an abelian group may be viewed as a generalization of these examples. Abelian groups are named after Niels Henrik Abel.
The concept of an abelian group underlies many fundamental algebraic structures, such as fields, rings, vector spaces, and algebras. The theory of abelian groups is generally simpler than that of their non-abelian counterparts, and finite abelian groups are very well understood and fully classified.
Definition
An abelian group is a set , together with an operation ･ , that combines any two elements and of to form another element of denoted . The symbol ･ is a general placeholder for a concretely given operation. To qualify as an abelian group, the set and operation, , must satisfy four requirements known as the abelian group axioms (some authors include in the axioms some properties that belong to the definition of an operation: namely that the operation is defined for any ordered pair of elements of , that the result is well-defined, and that the result belongs to ):
Associativity For all , , and in , the equation holds.
Identity element There exists an element in , such that for all elements in , the equation holds.
Inverse element For each in there exists an element in such that , where is the identity element.
Commutativity For all , in , .
A group in which the group operation is not commutative is called a "non-abelian group" or "non-commutative group".
Facts
Notation
There are two main notational conventions for abelian groups – additive and multiplicative.
Generally, the multiplicative notation is the usual notation for groups, while the additive notation is the usual notation for modules and rings. The additive notation may also be used to emphasize that a particular group is abelian, whenever both abelian and non-abelian groups are considered, some notable exceptions being near-rings and partially ordered groups, where an operation is written additively even when non-abelian. | Abelian group | Wikipedia | 479 | 2974 | https://en.wikipedia.org/wiki/Abelian%20group | Mathematics | Algebra | null |
Multiplication table
To verify that a finite group is abelian, a table (matrix) – known as a Cayley table – can be constructed in a similar fashion to a multiplication table. If the group is under the the entry of this table contains the product .
The group is abelian if and only if this table is symmetric about the main diagonal. This is true since the group is abelian iff for all , which is iff the entry of the table equals the entry for all , i.e. the table is symmetric about the main diagonal.
Examples
For the integers and the operation addition , denoted , the operation + combines any two integers to form a third integer, addition is associative, zero is the additive identity, every integer has an additive inverse, , and the addition operation is commutative since for any two integers and .
Every cyclic group is abelian, because if , are in , then . Thus the integers, , form an abelian group under addition, as do the integers modulo , .
Every ring is an abelian group with respect to its addition operation. In a commutative ring the invertible elements, or units, form an abelian multiplicative group. In particular, the real numbers are an abelian group under addition, and the nonzero real numbers are an abelian group under multiplication.
Every subgroup of an abelian group is normal, so each subgroup gives rise to a quotient group. Subgroups, quotients, and direct sums of abelian groups are again abelian. The finite simple abelian groups are exactly the cyclic groups of prime order.
The concepts of abelian group and -module agree. More specifically, every -module is an abelian group with its operation of addition, and every abelian group is a module over the ring of integers in a unique way.
In general, matrices, even invertible matrices, do not form an abelian group under multiplication because matrix multiplication is generally not commutative. However, some groups of matrices are abelian groups under matrix multiplication – one example is the group of rotation matrices.
Historical remarks
Camille Jordan named abelian groups after Norwegian mathematician Niels Henrik Abel, as Abel had found that the commutativity of the group of a polynomial implies that the roots of the polynomial can be calculated by using radicals. | Abelian group | Wikipedia | 477 | 2974 | https://en.wikipedia.org/wiki/Abelian%20group | Mathematics | Algebra | null |
Properties
If is a natural number and is an element of an abelian group written additively, then can be defined as ( summands) and . In this way, becomes a module over the ring of integers. In fact, the modules over can be identified with the abelian groups.
Theorems about abelian groups (i.e. modules over the principal ideal domain ) can often be generalized to theorems about modules over an arbitrary principal ideal domain. A typical example is the classification of finitely generated abelian groups which is a specialization of the structure theorem for finitely generated modules over a principal ideal domain. In the case of finitely generated abelian groups, this theorem guarantees that an abelian group splits as a direct sum of a torsion group and a free abelian group. The former may be written as a direct sum of finitely many groups of the form for prime, and the latter is a direct sum of finitely many copies of .
If are two group homomorphisms between abelian groups, then their sum , defined by , is again a homomorphism. (This is not true if is a non-abelian group.) The set of all group homomorphisms from to is therefore an abelian group in its own right.
Somewhat akin to the dimension of vector spaces, every abelian group has a rank. It is defined as the maximal cardinality of a set of linearly independent (over the integers) elements of the group. Finite abelian groups and torsion groups have rank zero, and every abelian group of rank zero is a torsion group. The integers and the rational numbers have rank one, as well as every nonzero additive subgroup of the rationals. On the other hand, the multiplicative group of the nonzero rationals has an infinite rank, as it is a free abelian group with the set of the prime numbers as a basis (this results from the fundamental theorem of arithmetic).
The center of a group is the set of elements that commute with every element of . A group is abelian if and only if it is equal to its center . The center of a group is always a characteristic abelian subgroup of . If the quotient group of a group by its center is cyclic then is abelian. | Abelian group | Wikipedia | 466 | 2974 | https://en.wikipedia.org/wiki/Abelian%20group | Mathematics | Algebra | null |
Finite abelian groups
Cyclic groups of integers modulo , , were among the first examples of groups. It turns out that an arbitrary finite abelian group is isomorphic to a direct sum of finite cyclic groups of prime power order, and these orders are uniquely determined, forming a complete system of invariants. The automorphism group of a finite abelian group can be described directly in terms of these invariants. The theory had been first developed in the 1879 paper of Georg Frobenius and Ludwig Stickelberger and later was both simplified and generalized to finitely generated modules over a principal ideal domain, forming an important chapter of linear algebra.
Any group of prime order is isomorphic to a cyclic group and therefore abelian. Any group whose order is a square of a prime number is also abelian. In fact, for every prime number there are (up to isomorphism) exactly two groups of order , namely and .
Classification
The fundamental theorem of finite abelian groups states that every finite abelian group can be expressed as the direct sum of cyclic subgroups of prime-power order; it is also known as the basis theorem for finite abelian groups. Moreover, automorphism groups of cyclic groups are examples of abelian groups. This is generalized by the fundamental theorem of finitely generated abelian groups, with finite groups being the special case when G has zero rank; this in turn admits numerous further generalizations.
The classification was proven by Leopold Kronecker in 1870, though it was not stated in modern group-theoretic terms until later, and was preceded by a similar classification of quadratic forms by Carl Friedrich Gauss in 1801; see history for details.
The cyclic group of order is isomorphic to the direct sum of and if and only if and are coprime. It follows that any finite abelian group is isomorphic to a direct sum of the form
in either of the following canonical ways:
the numbers are powers of (not necessarily distinct) primes,
or divides , which divides , and so on up to .
For example, can be expressed as the direct sum of two cyclic subgroups of order 3 and 5: . The same can be said for any abelian group of order 15, leading to the remarkable conclusion that all abelian groups of order 15 are isomorphic.
For another example, every abelian group of order 8 is isomorphic to either (the integers 0 to 7 under addition modulo 8), (the odd integers 1 to 15 under multiplication modulo 16), or . | Abelian group | Wikipedia | 509 | 2974 | https://en.wikipedia.org/wiki/Abelian%20group | Mathematics | Algebra | null |
Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventive surgery for such problems. A special case is that of congenital amputation, a congenital disorder, where fetal limbs have been cut off by constrictive bands. In some countries, judicial amputation is currently used to punish people who commit crimes. Amputation has also been used as a tactic in war and acts of terrorism; it may also occur as a war injury. In some cultures and religions, minor amputations or mutilations are considered a ritual accomplishment. When done by a person, the person executing the amputation is an amputator. The oldest evidence of this practice comes from a skeleton found buried in Liang Tebo cave, East Kalimantan, Indonesian Borneo dating back to at least 31,000 years ago, where it was done when the amputee was a young child.
Types
Leg
Lower limb amputations can be divided into two broad categories: minor and major amputations. Minor amputations generally refer to the amputation of digits. Major amputations are commonly below-knee- or above-knee amputations. Common partial foot amputations include the Chopart, Lisfranc, and ray amputations.
Common forms of ankle disarticulations include Pyrogoff, Boyd, and Syme amputations. A less common major amputation is the Van Nes rotation, or rotationplasty, i.e. the turning around and reattachment of the foot to allow the ankle joint to take over the function of the knee.
Types of amputations include: | Amputation | Wikipedia | 377 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
partial foot amputation amputation of the lower limb distal to the ankle joint
ankle disarticulation amputation of the lower limb at the ankle joint
trans-tibial amputation amputation of the lower limb between the knee joint and the ankle joint, commonly referred to as a below-knee amputation
knee disarticulation amputation of the lower limb at the knee joint
trans-femoral amputation amputation of the lower limb between the hip joint and the knee joint, commonly referred to an above-knee amputation
hip disarticulation amputation of the lower limb at the hip joint
trans-pelvic disarticulation amputation of the whole lower limb together with all or part of the pelvis, also known as a hemipelvectomy or hindquarter amputation
Arm
Types of upper extremity amputations include:
partial hand amputation
wrist disarticulation
trans-radial amputation, commonly referred to as below-elbow or forearm amputation
elbow disarticulation
trans-humeral amputation, commonly referred to as above-elbow amputation
shoulder disarticulation
forequarter amputation
A variant of the trans-radial amputation is the Krukenberg procedure in which the radius and ulna are used to create a stump capable of a pincer action.
Other
Facial amputations include but are not limited to:
amputation of the ears
amputation of the nose (rhinotomy)
amputation of the tongue (glossectomy).
amputation of the eyes (enucleation).
amputation of the teeth (Dental evulsion). Removal of teeth, mainly incisors, is or was practiced by some cultures for ritual purposes (for instance in the Iberomaurusian culture of Neolithic North Africa).
Breasts:
amputation of the breasts (mastectomy).
Genitals:
amputation of the testicles (castration).
amputation of the penis (penectomy).
amputation of the foreskin (circumcision).
amputation of the clitoris (clitoridectomy).
Hemicorporectomy, or amputation at the waist, and decapitation, or amputation at the neck, are the most radical amputations.
Genital modification and mutilation may involve amputating tissue, although not necessarily as a result of injury or disease.
Self-amputation | Amputation | Wikipedia | 494 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
In some rare cases when a person has become trapped in a deserted place, with no means of communication or hope of rescue, the victim has amputated their own limb. The most notable case of this is Aron Ralston, a hiker who amputated his own right forearm after it was pinned by a boulder in a hiking accident and he was unable to free himself for over five days.
Body integrity identity disorder is a psychological condition in which an individual feels compelled to remove one or more of their body parts, usually a limb. In some cases, that individual may take drastic measures to remove the offending appendages, either by causing irreparable damage to the limb so that medical intervention cannot save the limb, or by causing the limb to be severed.
Urgent
In surgery, a guillotine amputation is an amputation performed without closure of the skin in an urgent setting. Typical indications include catastrophic trauma or infection control in the setting of infected gangrene. A guillotine amputation is typically followed with a more time-consuming, definitive amputation such as an above or below knee amputation.
Causes
Circulatory disorders
Diabetic vasculopathy
Sepsis with peripheral necrosis
Peripheral artery disease which can lead to gangrene
A severe deep vein thrombosis (phlegmasia cerulea dolens) can cause compartment syndrome and gangrene
Neoplasm
Cancerous bone or soft tissue tumors (e.g. osteosarcoma, chondrosarcoma, fibrosarcoma, epithelioid sarcoma, Ewing's sarcoma, synovial sarcoma, sacrococcygeal teratoma, liposarcoma), melanoma
Trauma
Severe limb injuries in which the efforts to save the limb fail or the limb cannot be saved.
Traumatic amputation (an unexpected amputation that occurs at the scene of an accident, where the limb is partially or entirely severed as a direct result of the accident, for example, a finger that is severed from the blade of a table saw)
Amputation in utero (Amniotic band)
Congenital anomalies
Deformities of digits and/or limbs (e.g., proximal femoral focal deficiency, Fibular hemimelia)
Extra digits and/or limbs (e.g., polydactyly) | Amputation | Wikipedia | 494 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
Infection
Bone infection (osteomyelitis) and/or diabetic foot infections
Gangrene
Trench foot
Necrosis
Meningococcal meningitis
Streptococcus
Vibrio vulnificus
Necrotizing fasciitis
Gas gangrene
Legionella
Influenza A Virus
Animal bites
Sepsis
Bubonic plague
Frostbite
Frostbite is a cold-related injury occurring when an area (typically a limb or other extremity) is exposed to extreme low temperatures, causing the freezing of the skin or other tissues. Its pathophysiology involves the formation of ice crystals upon freezing and blood clots upon thawing, leading to cell damage and cell death. Treatment of severe frostbite may require surgical amputation of the affected tissue or limb; if there is deep injury autoamputation may occur.
Athletic performance
Sometimes professional athletes may choose to have a non-essential digit amputated to relieve chronic pain and impaired performance.
Australian Rules footballer Daniel Chick elected to have his left ring finger amputated as chronic pain and injury was limiting his performance.
Rugby union player Jone Tawake also had a finger removed.
National Football League safety Ronnie Lott had the tip of his little finger removed after it was damaged in the 1985 NFL season.
Criminal penalties | Amputation | Wikipedia | 262 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
According to Quran 5:38, the punishment for stealing is the amputation of the hand. Under Sharia law, after repeated offense, the foot may also be cut off. This is still in practice today in countries like Brunei, the United Arab Emirates, Iran, Saudi Arabia, Yemen, and 11 of the 36 states within Nigeria.
Cross-amputation is one of the Hudud punishments prescribed under Islamic jurisprudence (Sharia law) and involves cutting off the right hand and left foot of the alleged transgressor. The scriptural authority for the double amputation procedure is in the Quran (surah 5.33-34) which stipulates: The severe punishment, for "highway robbery (hirabah, qat' al-tariq) and civil disturbance against Islam", is usually carried out in a single session in public, without anaesthetic and using a sword. The ancient punishment is practised in Islamic countries such as Saudi Arabia; Sudan; Somalia; Mauritania, the Maldives; Iran; Taliban-era Afghanistan and Yemen.
In 1779, Thomas Jefferson proposed a bill to the Virginia Assembly that ostensibly would have replaced capital punishment with other penalties, including amputation, for certain crimes, although not all were really punishable by death at the time. For the crimes of rape, sodomy, and polygamy (the latter removed from a later version), the punishment was to be castration for men or rhinotomy for women. For intentional maiming, the bill specified literal eye for an eye retribution. The bill never passed, due to the combination of its perceived barbarity in some parts and perceived leniency in others.
From the 16th century, English law provided for cutting off a hand as punishment for striking someone inside a courtroom. Thomas Jefferson's punishments revision bill also intended to repeal this.
As of 2021, this form of punishment is controversial, as most modern cultures consider it to be morally abhorrent, as it has the effect of permanently disabling a person and constitutes torture. It is thus seen as grossly disproportionate for crimes less than those such as murder.
Surgery
Method | Amputation | Wikipedia | 440 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
Surgeons performing an amputation have to first ligate the supplying artery and vein, so as to prevent hemorrhage (bleeding). The muscles are transected, and finally, the bone is sawed through with an oscillating saw. Sharp and rough edges of bones are filed, skin and muscle flaps are then transposed over the stump, occasionally with the insertion of elements to attach a prosthesis.
Distal stabilisation of muscles is often performed. This allows effective muscle contraction which reduces atrophy, allows functional use of the stump and maintains soft tissue coverage of the remnant bone. The preferred stabilisation technique is myodesis where the muscle is attached to the bone or its periosteum. In joint disarticulation amputations tenodesis may be used where the muscle tendon is attached to the bone. Muscles are attached under similar tension to normal physiological conditions.
An experimental technique known as the "Ewing amputation" aims to improve post-amputation proprioception. Another technique with similar goals, which has been tested in a clinical trial, is Agonist-antagonist Myoneural Interface (AMI).
In 1920, Dr. Janos Ertl Sr. of Hungary, developed the Ertl procedure in order to return a high number of amputees to the work force. The Ertl technique, an osteomyoplastic procedure for transtibial amputation, can be used to create a highly functional residual limb. Creation of a tibiofibular bone bridge provides a stable, broad tibiofibular articulation that may be capable of some distal weight bearing. Several different modified techniques and fibular bridge fixation methods have been used; however, no current evidence exists regarding comparison of the different techniques.
Post-operative management
A 2019 Cochrane systematic review aimed to determine whether rigid dressings were more effective than soft dressings in helping wounds heal following transtibial (below the knee) amputations. Due to the limited and very low certainty evidence available, the authors concluded that it was uncertain what the benefits and harms were for each dressing type. They recommended that clinicians consider the pros and cons of each dressing type on a case-by-case basis: rigid dressings may potentially benefit patients who have a high risk of falls; soft dressings may potentially benefit patients who have poor skin integrity. | Amputation | Wikipedia | 482 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
A 2017 review found that the use of rigid removable dressings (RRD's) in trans-tibial amputations, rather than soft bandaging, improved healing time, reduced edema, prevented knee flexion contractures and reduced complications, including further amputation, from external trauma such as falls onto the stump.
Post-operative management, in addition to wound healing, considers maintenance of limb strength, joint range, edema management, preservation of the intact limb (if applicable) and stump desensitization.
Trauma
Traumatic amputation is the partial or total avulsion of a part of a body during a serious accident, like traffic, labor, or combat.
Traumatic amputation of a human limb, either partial or total, creates the immediate danger of death from blood loss.
Orthopedic surgeons often assess the severity of different injuries using the Mangled Extremity Severity Score. Given different clinical and situational factors, they can predict the likelihood of amputation. This is especially useful for emergency physicians to quickly evaluate patients and decide on consultations.
Causes
Traumatic amputation is uncommon in humans (1 per 20,804 population per year). Loss of limb usually happens immediately during the accident, but sometimes a few days later after medical complications. Statistically, the most common causes of traumatic amputations are:
Vehicle accidents (cars, motorcycles, bicycles, trains, etc.)
Labor accidents (equipment, instruments, cylinders, chainsaws, press machines, meat machines, wood machines, etc.)
Agricultural accidents, with machines and mower equipment
Electric shock hazards
Firearms, bladed weapons, explosives
Violent rupture of ship rope or industry wire rope
Ring traction (ring amputation, de-gloving injuries)
Building doors and car doors
Animal attacks
Gas cylinder explosions
Other rare accidents
Treatment
The development of the science of microsurgery over the last 40 years has provided several treatment options for a traumatic amputation, depending on the patient's specific trauma and clinical situation:
1st choice: Surgical amputation - break - prosthesis
2nd choice: Surgical amputation - transplantation of other tissue - plastic reconstruction.
3rd choice: Replantation - reconnection - revascularisation of amputated limb, by microscope (after 1969)
4th choice: Transplantation of cadaveric hand (after 2000)
Epidemiology | Amputation | Wikipedia | 477 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
In the United States in 1999, there were 14,420 non-fatal traumatic amputations according to the American Statistical Association. Of these, 4,435 occurred as a result of traffic and transportation accidents and 9,985 were due to labor accidents. Of all traumatic amputations, the distribution percentage is 30.75% for traffic accidents and 69.24% for labor accidents.
The population of the United States in 1999 was about 300,000,000, so the conclusion is that there is one amputation per 20,804 persons per year. In the group of labor amputations, 53% occurred in laborers and technicians, 30% in production and service workers, 16% in silviculture and fishery workers.
A study found that in 2010, 22.8% of patients undergoing amputation of a lower extremity in the United States were readmitted to the hospital within 30 days.
In 2017, an estimated 57.7 million people globally were living with existing traumatic limb injuries. Of these 57.7 million, the leading causes of amputation "were falls (36.2%), road injuries (15.7%), other transportation injuries (11.2%), and mechanical forces (10.4%)."
On 2 August 2023, an investigation by The Wall Street Journal found that Ukrainian medical amputations in the war came to between 20,000 and 50,000 including both military and civilians. In comparison, during World War One 41,000 British and 67,000 Germans needed amputations.
Prevention
Methods in preventing amputation, limb-sparing techniques, depend on the problems that might cause amputations to be necessary. Chronic infections, often caused by diabetes or decubitus ulcers in bedridden patients, are common causes of infections that lead to gangrene, which, when widespread, necessitates amputation.
There are two key challenges: first, many patients have impaired circulation in their extremities, and second, they have difficulty curing infections in limbs with poor blood circulation.
Crush injuries where there is extensive tissue damage and poor circulation also benefit from hyperbaric oxygen therapy (HBOT). The high level of oxygenation and revascularization speed up recovery times and prevent infections. | Amputation | Wikipedia | 471 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
A study found that the patented method called Circulator Boot achieved significant results in prevention of amputation in patients with diabetes and arteriosclerosis. Another study found it also effective for healing limb ulcers caused by peripheral vascular disease. The boot checks the heart rhythm and compresses the limb between heartbeats; the compression helps cure the wounds in the walls of veins and arteries, and helps to push the blood back to the heart.
For victims of trauma, advances in microsurgery in the 1970s have made replantations of severed body parts possible.
The establishment of laws, rules, and guidelines, and employment of modern equipment help protect people from traumatic amputations.
Prognosis
The individual may experience psychological trauma and emotional discomfort. The stump will remain an area of reduced mechanical stability. Limb loss can present significant or even drastic practical limitations.
A large proportion of amputees (50–80%) experience the phenomenon of phantom limbs; they feel body parts that are no longer there. These limbs can itch, ache, burn, feel tense, dry or wet, locked in or trapped or they can feel as if they are moving. Some scientists believe it has to do with a kind of neural map that the brain has of the body, which sends information to the rest of the brain about limbs regardless of their existence. Phantom sensations and phantom pain may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast, extraction of a tooth (phantom tooth pain) or removal of an eye (phantom eye syndrome).
A similar phenomenon is unexplained sensation in a body part unrelated to the amputated limb. It has been hypothesized that the portion of the brain responsible for processing stimulation from amputated limbs, being deprived of input, expands into the surrounding brain, (Phantoms in the Brain: V.S. Ramachandran and Sandra Blakeslee) such that an individual who has had an arm amputated will experience unexplained pressure or movement on his face or head.
In many cases, the phantom limb aids in adaptation to a prosthesis, as it permits the person to experience proprioception of the prosthetic limb. To support improved resistance or usability, comfort or healing, some type of stump socks may be worn instead of or as part of wearing a prosthesis. | Amputation | Wikipedia | 493 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
Another side effect can be heterotopic ossification, especially when a bone injury is combined with a head injury. The brain signals the bone to grow instead of scar tissue to form, and nodules and other growth can interfere with prosthetics and sometimes require further operations. This type of injury has been especially common among soldiers wounded by improvised explosive devices in the Iraq War.
Due to technological advances in prosthetics, many amputees live active lives with little restriction. Organizations such as the Challenged Athletes Foundation have been developed to give amputees the opportunity to be involved in athletics and adaptive sports such as amputee soccer.
Nearly half of the individuals who have an amputation due to vascular disease will die within 5 years, usually secondary to the extensive co-morbidities rather than due to direct consequences of amputation. This is higher than the five year mortality rates for breast cancer, colon cancer, and prostate cancer. Of persons with diabetes who have a lower extremity amputation, up to 55% will require amputation of the second leg within two to three years.
Etymology
The word amputation is borrowed from Latin amputātus, past participle of amputāre "to prune back (a plant), prune away, remove by cutting (unwanted parts or features), cut off (a branch, limb, body part)," from am-, assimilated variant of amb- "about, around" + putāre "to prune, make clean or tidy, scour (wool)". The English word "Poes" was first applied to surgery in the 17th century, possibly first in Peter Lowe's A discourse of the Whole Art of Chirurgerie (published in either 1597 or 1612); his work was derived from 16th-century French texts and early English writers also used the words "extirpation" (16th-century French texts tended to use extirper), "disarticulation", and "dismemberment" (from the Old French desmembrer and a more common term before the 17th century for limb loss or removal), or simply "cutting", but by the end of the 17th century "amputation" had come to dominate as the accepted medical term. | Amputation | Wikipedia | 470 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
Notable cases
Patch Adams
Rick Allen
Douglas Bader
Götz of the Iron Hand
Carl Brashear
Lisa Bufano
Roberto Carlos
Tammy Duckworth
Kalamandalam Sankaran Embranthiri
Terry Fox
Zach Gowen
Pete Gray
Shaquem Griffin
Robert David Hall
Bethany Hamilton
Hugh Herr
Frida Kahlo
Ronnie Lott
Hari Budha Magar
Aimee Mullins
Oscar Pistorius
Amy Purdy
Aron Ralston
Hans-Ulrich Rudel
Alex Zanardi | Amputation | Wikipedia | 93 | 2992 | https://en.wikipedia.org/wiki/Amputation | Biology and health sciences | Medical procedures | null |
Archaeopteryx (; ), sometimes referred to by its German name, "" ( Primeval Bird) is a genus of bird-like dinosaurs. The name derives from the ancient Greek (archaīos), meaning "ancient", and (ptéryx), meaning "feather" or "wing". Between the late 19th century and the early 21st century, Archaeopteryx was generally accepted by palaeontologists and popular reference books as the oldest known bird (member of the group Avialae). Older potential avialans have since been identified, including Anchiornis, Xiaotingia, and Aurornis.
Archaeopteryx lived in the Late Jurassic around 150 million years ago, in what is now southern Germany, during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Similar in size to a Eurasian magpie, with the largest individuals possibly attaining the size of a raven, the largest species of Archaeopteryx could grow to about in length. Despite their small size, broad wings, and inferred ability to fly or glide, Archaeopteryx had more in common with other small Mesozoic dinosaurs than with modern birds. In particular, they shared the following features with the dromaeosaurids and troodontids: jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggest warm-bloodedness), and various features of the skeleton.
These features make Archaeopteryx a clear candidate for a transitional fossil between non-avian dinosaurs and avian dinosaurs (birds). Thus, Archaeopteryx plays an important role, not only in the study of the origin of birds, but in the study of dinosaurs. It was named from a single feather in 1861, the identity of which has been controversial. That same year, the first complete specimen of Archaeopteryx was announced. Over the years, eleven more fossils of Archaeopteryx have surfaced. Despite variation among these fossils, most experts regard all the remains that have been discovered as belonging to a single species, although this is still debated. | Archaeopteryx | Wikipedia | 469 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Most of these twelve fossils include impressions of feathers. Because these feathers are of an advanced form (flight feathers), these fossils are evidence that the evolution of feathers began before the Late Jurassic. The type specimen of Archaeopteryx was discovered just two years after Charles Darwin published On the Origin of Species. Archaeopteryx seemed to confirm Darwin's theories and has since become a key piece of evidence for the origin of birds, the transitional fossils debate, and confirmation of evolution. Archaeopteryx was long considered to be the beginning of the evolutionary tree of birds. However, in recent years, the discovery of several small, feathered dinosaurs has created a mystery for palaeontologists, raising questions about which animals are the ancestors of modern birds and which are their relatives.
History of discovery
Over the years, fourteen body fossil specimens of Archaeopteryx have been found. All of the fossils come from the limestone deposits, quarried for centuries, near , Germany. These quarries excavate sediments from the Solnhofen Limestone formation and related units. The initial specimen was the first dinosaur to be discovered with feathers.
The initial discovery, a single feather, was unearthed in 1860 or 1861 and described in 1861 by . It is now in the Natural History Museum of Berlin. Though it was the initial holotype, there were indications that it might not have been from the same animal as the body fossils. In 2019 it was reported that laser imaging had revealed the structure of the quill (which had not been visible since some time after the feather was described), and that the feather was inconsistent with the morphology of all other Archaeopteryx feathers known, leading to the conclusion that it originated from another dinosaur. This conclusion was challenged in 2020 as being unlikely; the feather was identified on the basis of morphology as most likely having been an upper major primary covert feather. | Archaeopteryx | Wikipedia | 384 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The first skeleton, known as the London Specimen (BMNH 37001), was unearthed in 1861 near , Germany, and perhaps given to local physician in return for medical services. He then sold it for £700 (roughly £83,000 in 2020) to the Natural History Museum in London, where it remains. Missing most of its head and neck, it was described in 1863 by Richard Owen as Archaeopteryx macrura, allowing for the possibility it did not belong to the same species as the feather. In the subsequent fourth edition of his On the Origin of Species, Charles Darwin described how some authors had maintained "that the whole class of birds came suddenly into existence during the eocene period; but now we know, on the authority of Professor Owen, that a bird certainly lived during the deposition of the upper greensand; and still more recently, that strange bird, the Archaeopteryx, with a long lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been discovered in the oolitic slates of Solnhofen. Hardly any recent discovery shows more forcibly than this how little we as yet know of the former inhabitants of the world."
The Greek word () means 'ancient, primeval'. primarily means 'wing', but it can also be just 'feather'. Meyer suggested this in his description. At first he referred to a single feather which appeared to resemble a modern bird's remex (wing feather), but he had heard of and been shown a rough sketch of the London specimen, to which he referred as a "" ("skeleton of an animal covered in similar feathers"). In German, this ambiguity is resolved by the term which does not necessarily mean a wing used for flying. was the favoured translation of Archaeopteryx among German scholars in the late nineteenth century. In English, 'ancient pinion' offers a rough approximation to this.
Since then, twelve specimens have been recovered: | Archaeopteryx | Wikipedia | 418 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The Berlin Specimen (HMN 1880/81) was discovered in 1874 or 1875 on the Blumenberg near , Germany, by farmer Jakob Niemeyer. He sold this precious fossil for the money to buy a cow in 1876, to innkeeper Johann Dörr, who again sold it to Ernst Otto Häberlein, the son of K. Häberlein. Placed on sale between 1877 and 1881, with potential buyers including O. C. Marsh of Yale University's Peabody Museum, it eventually was bought for 20,000 Goldmark by the Berlin's Natural History Museum, where it now is displayed. The transaction was financed by Ernst Werner von Siemens, founder of the company that bears his name. Described in 1884 by Wilhelm Dames, it is the most complete specimen, and the first with a complete head. In 1897 it was named by Dames as a new species, A. siemensii; though often considered a synonym of A. lithographica, several 21st century studies have concluded that it is a distinct species which includes the Berlin, Munich, and Thermopolis specimens.
Composed of a torso, the Maxberg Specimen (S5) was discovered in 1956 near Langenaltheim; it was brought to the attention of professor Florian Heller in 1958 and described by him in 1959. The specimen is missing its head and tail, although the rest of the skeleton is mostly intact. Although it was once exhibited at the Maxberg Museum in Solnhofen, it is currently missing. It belonged to Eduard Opitsch, who loaned it to the museum until 1974. After his death in 1991, it was discovered that the specimen was missing and may have been stolen or sold.
The Haarlem Specimen (TM 6428/29, also known as the Teylers Specimen) was discovered in 1855 near , Germany, and described as a Pterodactylus crassipes in 1857 by Meyer. It was reclassified in 1970 by John Ostrom and is currently located at the Teylers Museum in Haarlem, the Netherlands. It was the very first specimen found, but was incorrectly classified at the time. It is also one of the least complete specimens, consisting mostly of limb bones, isolated cervical vertebrae, and ribs. In 2017 it was named as a separate genus Ostromia, considered more closely related to Anchiornis from China. | Archaeopteryx | Wikipedia | 483 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The Eichstätt Specimen (JM 2257) was discovered in 1951 near Workerszell, Germany, and described by Peter Wellnhofer in 1974. Currently located at the Jura Museum in Eichstätt, Germany, it is the smallest known specimen and has the second-best head. It is possibly a separate genus (Jurapteryx recurva) or species (A. recurva).
The Solnhofen Specimen (unnumbered specimen) was discovered in the 1970s near Eichstätt, Germany, and described in 1988 by Wellnhofer. Currently located at the Bürgermeister-Müller-Museum in Solnhofen, it originally was classified as Compsognathus by an amateur collector, the same mayor Friedrich Müller after which the museum is named. It is the largest specimen known and may belong to a separate genus and species, Wellnhoferia grandis. It is missing only portions of the neck, tail, backbone, and head.
The Munich Specimen (BSP 1999 I 50, formerly known as the Solenhofer-Aktien-Verein Specimen) was discovered on 3 August 1992 near Langenaltheim and described in 1993 by Wellnhofer. It is currently located at the Paläontologisches Museum München in Munich, to which it was sold in 1999 for 1.9 million Deutschmark. What was initially believed to be a bony sternum turned out to be part of the coracoid, but a cartilaginous sternum may have been present. Only the front of its face is missing. It has been used as the basis for a distinct species, A. bavarica, but more recent studies suggest it belongs to A. siemensii. | Archaeopteryx | Wikipedia | 361 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
An eighth, fragmentary specimen was discovered in 1990 in the younger Mörnsheim Formation at Daiting, Suevia. Therefore, it is known as the Daiting Specimen, and had been known since 1996 only from a cast, briefly shown at the Naturkundemuseum in Bamberg. The original was purchased by palaeontologist Raimund Albertsdörfer in 2009. It was on display for the first time with six other original fossils of Archaeopteryx at the Munich Mineral Show in October 2009. The Daiting Specimen was subsequently named Archaeopteryx albersdoerferi by Kundrat et al. (2018). After a lengthy period in a closed private collection, it was moved to the Museum of Evolution at Knuthenborg Safaripark (Denmark) in 2022, where it has since been on display and also been made available for researchers.
Another fragmentary fossil was found in 2000. It is in private possession and, since 2004, on loan to the Bürgermeister-Müller Museum in Solnhofen, so it is called the Bürgermeister-Müller Specimen; the institute itself officially refers to it as the "Exemplar of the families Ottman & Steil, Solnhofen". As the fragment represents the remains of a single wing of Archaeopteryx, it is colloquially known as "chicken wing". | Archaeopteryx | Wikipedia | 283 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Long in a private collection in Switzerland, the Thermopolis Specimen (WDC CSG 100) was discovered in Bavaria and described in 2005 by Mayr, Pohl, and Peters. Donated to the Wyoming Dinosaur Center in Thermopolis, Wyoming, it has the best-preserved head and feet; most of the neck and the lower jaw have not been preserved. The "Thermopolis" specimen was described on 2 December 2005 Science journal article as "A well-preserved Archaeopteryx specimen with theropod features"; it shows that Archaeopteryx lacked a reversed toe—a universal feature of birds—limiting its ability to perch on branches and implying a terrestrial or trunk-climbing lifestyle. This has been interpreted as evidence of theropod ancestry. In 1988, Gregory S. Paul claimed to have found evidence of a hyperextensible second toe, but this was not verified and accepted by other scientists until the Thermopolis specimen was described. "Until now, the feature was thought to belong only to the species' close relatives, the deinonychosaurs." The Thermopolis Specimen was assigned to Archaeopteryx siemensii in 2007. The specimen is considered to represent the most complete and best-preserved Archaeopteryx remains yet.
The discovery of an eleventh specimen was announced in 2011; it was described in 2014. It is one of the more complete specimens, but is missing much of the skull and one forelimb. It is privately owned and has yet to be given a name. Palaeontologists of the Ludwig Maximilian University of Munich studied the specimen, which revealed previously unknown features of the plumage, such as feathers on both the upper and lower legs and metatarsus, and the only preserved tail tip.
A twelfth specimen had been discovered by an amateur collector in 2010 at the Schamhaupten quarry, but the finding was only announced in February 2014. It was scientifically described in 2018. It represents a complete and mostly articulated skeleton with skull. It is the only specimen lacking preserved feathers. It is from the Painten Formation and somewhat older than the other specimens. | Archaeopteryx | Wikipedia | 439 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The existence of a thirteenth specimen (the Chicago specimen) was announced in 2024 by the Field Museum in Chicago, US. One of two specimens in an institution outside Europe, the specimen was originally identified in a private collection in Switzerland, and had been acquired by these collectors in 1990, prior to Germany's 2015 ban on exporting Archaeopteryx specimens. The specimen was acquired by the Field Museum in 2022, and went on public display in 2024 following two years of preparation. The specimen is to be studied by famed paleornithologist Jingmai O'Connor.
A fourteenth specimen, SMNK-PAL 10,000, was published in January 2025, this one from the Mörnsheim Formation. It preserves the right forelimb, shoulder, and fragments of the other limbs, with various features of the shoulder and forelimb resembling Archaeopteryx more than any other avialan within the Mörnsheim Formation. However, due to the fragmentary nature of this specimen, it cannot be assigned to a specific species within Archaeopteryx.
Authenticity
Beginning in 1985, an amateur group including astronomer Fred Hoyle and physicist Lee Spetner, published a series of papers claiming that the feathers on the Berlin and London specimens of Archaeopteryx were forged. Their claims were repudiated by Alan J. Charig and others at the Natural History Museum in London. Most of their supposed evidence for a forgery was based on unfamiliarity with the processes of lithification; for example, they proposed that, based on the difference in texture associated with the feathers, feather impressions were applied to a thin layer of cement, without realizing that feathers themselves would have caused a textural difference. They also misinterpreted the fossils, claiming that the tail was forged as one large feather, when visibly this is not the case. In addition, they claimed that the other specimens of Archaeopteryx known at the time did not have feathers, which is incorrect; the Maxberg and Eichstätt specimens have obvious feathers.
They also expressed disbelief that slabs would split so smoothly, or that one half of a slab containing fossils would have good preservation, but not the counterslab. These are common properties of Solnhofen fossils, because the dead animals would fall onto hardened surfaces, which would form a natural plane for the future slabs to split along and would leave the bulk of the fossil on one side and little on the other. | Archaeopteryx | Wikipedia | 503 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Finally, the motives they suggested for a forgery are not strong, and are contradictory; one is that Richard Owen wanted to forge evidence in support of Charles Darwin's theory of evolution, which is unlikely given Owen's views toward Darwin and his theory. The other is that Owen wanted to set a trap for Darwin, hoping the latter would support the fossils so Owen could discredit him with the forgery; this is unlikely because Owen wrote a detailed paper on the London specimen, so such an action would certainly backfire.
Charig et al. pointed to the presence of hairline cracks in the slabs running through both rock and fossil impressions, and mineral growth over the slabs that had occurred before discovery and preparation, as evidence that the feathers were original. Spetner et al. then attempted to show that the cracks would have propagated naturally through their postulated cement layer, but neglected to account for the fact that the cracks were old and had been filled with calcite, and thus were not able to propagate. They also attempted to show the presence of cement on the London specimen through X-ray spectroscopy, and did find something that was not rock; it was not cement either, and is most probably a fragment of silicone rubber left behind when moulds were made of the specimen. Their suggestions have not been taken seriously by palaeontologists, as their evidence was largely based on misunderstandings of geology, and they never discussed the other feather-bearing specimens, which have increased in number since then. Charig et al. reported a discolouration: a dark band between two layers of limestone – they say it is the product of sedimentation. It is natural for limestone to take on the colour of its surroundings and most limestones are coloured (if not colour banded) to some degree, so the darkness was attributed to such impurities. They also mention that a complete absence of air bubbles in the rock slabs is further proof that the specimen is authentic.
Description
Most of the specimens of Archaeopteryx that have been discovered come from the Solnhofen limestone in Bavaria, southern Germany, which is a , a rare and remarkable geological formation known for its superbly detailed fossils laid down during the early Tithonian stage of the Jurassic period, approximately 150.8–148.5million years ago. | Archaeopteryx | Wikipedia | 475 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Archaeopteryx was roughly the size of a raven, with broad wings that were rounded at the ends and a long tail compared to its body length. It could reach up to in body length and in wingspan, with an estimated mass of . Archaeopteryx feathers, although less documented than its other features, were very similar in structure to modern-day bird feathers. Despite the presence of numerous avian features, Archaeopteryx had many non-avian theropod dinosaur characteristics. Unlike modern birds, Archaeopteryx had small teeth, as well as a long bony tail, features which Archaeopteryx shared with other dinosaurs of the time.
Because it displays features common to both birds and non-avian dinosaurs, Archaeopteryx has often been considered a link between them. In the 1970s, John Ostrom, following Thomas Henry Huxley's lead in 1868, argued that birds evolved within theropod dinosaurs and Archaeopteryx was a critical piece of evidence for this argument; it had several avian features, such as a wishbone, flight feathers, wings, and a partially reversed first toe along with dinosaur and theropod features. For instance, it has a long ascending process of the ankle bone, interdental plates, an obturator process of the ischium, and long chevrons in the tail. In particular, Ostrom found that Archaeopteryx was remarkably similar to the theropod family Dromaeosauridae.
Archaeopteryx had three separate digits on each fore-leg each ending with a "claw". Few birds have such features. Some birds, such as ducks, swans, Jacanas (Jacana sp.), and the hoatzin (Opisthocomus hoazin), have them concealed beneath their leg-feathers.
Plumage
Specimens of Archaeopteryx were most notable for their well-developed flight feathers. They were markedly asymmetrical and showed the structure of flight feathers in modern birds, with vanes given stability by a barb-barbule-barbicel arrangement. The tail feathers were less asymmetrical, again in line with the situation in modern birds and also had firm vanes. The thumb did not yet bear a separately movable tuft of stiff feathers. | Archaeopteryx | Wikipedia | 482 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The body plumage of Archaeopteryx is less well-documented and has only been properly researched in the well-preserved Berlin specimen. Thus, as more than one species seems to be involved, the research into the Berlin specimen's feathers does not necessarily hold true for the rest of the species of Archaeopteryx. In the Berlin specimen, there are "trousers" of well-developed feathers on the legs; some of these feathers seem to have a basic contour feather structure, but are somewhat decomposed (they lack barbicels as in ratites). In part they are firm and thus capable of supporting flight.
A patch of pennaceous feathers is found running along its back, which was quite similar to the contour feathers of the body plumage of modern birds in being symmetrical and firm, although not as stiff as the flight-related feathers. Apart from that, the feather traces in the Berlin specimen are limited to a sort of "proto-down" not dissimilar to that found in the dinosaur Sinosauropteryx: decomposed and fluffy, and possibly even appearing more like fur than feathers in life (although not in their microscopic structure). These occur on the remainder of the body—although some feathers did not fossilize and others were obliterated during preparation, leaving bare patches on specimens—and the lower neck.
There is no indication of feathering on the upper neck and head. While these conceivably may have been nude, this may still be an artefact of preservation. It appears that most Archaeopteryx specimens became embedded in anoxic sediment after drifting some time on their backs in the sea—the head, neck and the tail are generally bent downward, which suggests that the specimens had just started to rot when they were embedded, with tendons and muscle relaxing so that the characteristic shape (death pose) of the fossil specimens was achieved. This would mean that the skin already was softened and loose, which is bolstered by the fact that in some specimens the flight feathers were starting to detach at the point of embedding in the sediment. So it is hypothesized that the pertinent specimens moved along the sea bed in shallow water for some time before burial, the head and upper neck feathers sloughing off, while the more firmly attached tail feathers remained.
Colouration | Archaeopteryx | Wikipedia | 483 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
In 2011, graduate student Ryan Carney and colleagues performed the first colour study on an Archaeopteryx specimen. Using scanning electron microscopy technology and energy-dispersive X-ray analysis, the team was able to detect the structure of melanosomes in the isolated feather specimen described in 1861. The resultant measurements were then compared to those of 87modern bird species, and the original colour was calculated with a 95% likelihood to be black. The feather was determined to be black throughout, with heavier pigmentation in the distal tip. The feather studied was most probably a dorsal covert, which would have partly covered the primary feathers on the wings. The study does not mean that Archaeopteryx was entirely black, but suggests that it had some black colouration which included the coverts. Carney pointed out that this is consistent with what is known of modern flight characteristics, in that black melanosomes have structural properties that strengthen feathers for flight. In a 2013 study published in the Journal of Analytical Atomic Spectrometry, new analyses of Archaeopteryxs feathers revealed that the animal may have had complex light- and dark-coloured plumage, with heavier pigmentation in the distal tips and outer vanes. This analysis of colour distribution was based primarily on the distribution of sulphate within the fossil. An author on the previous Archaeopteryx colour study argued against the interpretation of such biomarkers as an indicator of eumelanin in the full Archaeopteryx specimen. Carney and other colleagues also argued against the 2013 study's interpretation of the sulphate and trace metals, and in a 2020 study published in Scientific Reports demonstrated that the isolated covert feather was entirely matte black (as opposed to black and white, or iridescent) and that the remaining "plumage patterns of Archaeopteryx remain unknown".
Classification | Archaeopteryx | Wikipedia | 380 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Today, fossils of the genus Archaeopteryx are usually assigned to one or two species, A. lithographica and A. siemensii, but their taxonomic history is complicated. Ten names have been published for the handful of specimens. As interpreted today, the name A. lithographica only referred to the single feather described by Meyer. In 1954 Gavin de Beer concluded that the London specimen was the holotype. In 1960, Swinton accordingly proposed that the name Archaeopteryx lithographica be placed on the official genera list making the alternative names Griphosaurus and Griphornis invalid. The ICZN, implicitly accepting De Beer's standpoint, did indeed suppress the plethora of alternative names initially proposed for the first skeleton specimens, which mainly resulted from the acrimonious dispute between Meyer and his opponent Johann Andreas Wagner (whose Griphosaurus problematicus—'problematic riddle-lizard'—was a vitriolic sneer at Meyer's Archaeopteryx). In addition, in 1977, the Commission ruled that the first species name of the Haarlem specimen, crassipes, described by Meyer as a pterosaur before its true nature was realized, was not to be given preference over lithographica in instances where scientists considered them to represent the same species.
It has been noted that the feather, the first specimen of Archaeopteryx described, does not correspond well with the flight-related feathers of Archaeopteryx. It certainly is a flight feather of a contemporary species, but its size and proportions indicate that it may belong to another, smaller species of feathered theropod, of which only this feather is known so far. As the feather had been designated the type specimen, the name Archaeopteryx should then no longer be applied to the skeletons, thus creating significant nomenclatorial confusion. In 2007, two sets of scientists therefore petitioned the ICZN requesting that the London specimen explicitly be made the type by designating it as the new holotype specimen, or neotype. This suggestion was upheld by the ICZN after four years of debate, and the London specimen was designated the neotype on 3 October 2011.
Below is a cladogram published in 2013 by Godefroit et al.
Species | Archaeopteryx | Wikipedia | 476 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
It has been argued that all the specimens belong to the same species, A. lithographica. Differences do exist among the specimens, and while some researchers regard these as due to the different ages of the specimens, some may be related to actual species diversity. In particular, the Munich, Eichstätt, Solnhofen, and Thermopolis specimens differ from the London, Berlin, and Haarlem specimens in being smaller or much larger, having different finger proportions, having more slender snouts lined with forward-pointing teeth, and the possible presence of a sternum. Due to these differences, most individual specimens have been given their own species name at one point or another. The Berlin specimen has been designated as Archaeornis siemensii, the Eichstätt specimen as Jurapteryx recurva, the Munich specimen as Archaeopteryx bavarica, and the Solnhofen specimen as Wellnhoferia grandis.
In 2007, a review of all well-preserved specimens including the then-newly discovered Thermopolis specimen concluded that two distinct species of Archaeopteryx could be supported: A. lithographica (consisting of at least the London and Solnhofen specimens), and A. siemensii (consisting of at least the Berlin, Munich, and Thermopolis specimens). The two species are distinguished primarily by large flexor tubercles on the foot claws in A. lithographica (the claws of A. siemensii specimens being relatively simple and straight). A. lithographica also had a constricted portion of the crown in some teeth and a stouter metatarsus. A supposed additional species, Wellnhoferia grandis (based on the Solnhofen specimen), seems to be indistinguishable from A. lithographica except in its larger size.
Synonyms | Archaeopteryx | Wikipedia | 393 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
If two names are given, the first denotes the original describer of the "species", the second the author on whom the given name combination is based. As always in zoological nomenclature, putting an author's name in parentheses denotes that the taxon was originally described in a different genus.
Archaeopteryx lithographica Meyer, 1861 [conserved name]
Archaeopterix lithographica Anon., 1861 [lapsus]
Griphosaurus problematicus Wagner, 1862 [rejected name 1961 per ICZN Opinion 607]
Griphornis longicaudatus Owen vide Woodward, 1862 [rejected name 1961 per ICZN Opinion 607]
Archaeopteryx macrura Owen, 1862 [rejected name 1961 per ICZN Opinion 607]
Archaeopteryx oweni Petronievics, 1917 [rejected name 1961 per ICZN Opinion 607]
Archaeopteryx recurva Howgate, 1984
Jurapteryx recurva (Howgate, 1984) Howgate, 1985
Wellnhoferia grandis Elżanowski, 2001
Archaeopteryx siemensii Dames, 1897
Archaeornis siemensii (Dames, 1897) Petronievics, 1917
Archaeopteryx bavarica Wellnhofer, 1993
"Archaeopteryx" vicensensis (Anon. fide Lambrecht, 1933) is a nomen nudum for what appears to be an undescribed pterosaur.
Phylogenetic position
Modern palaeontology has often classified Archaeopteryx as the most primitive bird. However, it is not thought to be a true ancestor of modern birds, but rather a close relative of that ancestor. Nonetheless, Archaeopteryx was often used as a model of the true ancestral bird. Several authors have done so. Lowe (1935) and Thulborn (1984) questioned whether Archaeopteryx truly was the first bird. They suggested that Archaeopteryx was a dinosaur that was no more closely related to birds than were other dinosaur groups. Kurzanov (1987) suggested that Avimimus was more likely to be the ancestor of all birds than Archaeopteryx. Barsbold (1983) and Zweers and Van den Berge (1997) noted that many maniraptoran lineages are extremely birdlike, and they suggested that different groups of birds may have descended from different dinosaur ancestors. | Archaeopteryx | Wikipedia | 507 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The discovery of the closely related Xiaotingia in 2011 led to new phylogenetic analyses that suggested that Archaeopteryx is a deinonychosaur rather than an avialan, and therefore, not a "bird" under most common uses of that term. A more thorough analysis was published soon after to test this hypothesis, and failed to arrive at the same result; it found Archaeopteryx in its traditional position at the base of Avialae, while Xiaotingia was recovered as a basal dromaeosaurid or troodontid. The authors of the follow-up study noted that uncertainties still exist, and that it may not be possible to state confidently whether or not Archaeopteryx is a member of Avialae or not, barring new and better specimens of relevant species.
Phylogenetic studies conducted by Senter, et al. (2012) and Turner, Makovicky, and Norell (2012) also found Archaeopteryx to be more closely related to living birds than to dromaeosaurids and troodontids. On the other hand, Godefroit et al. (2013) recovered Archaeopteryx as more closely related to dromaeosaurids and troodontids in the analysis included in their description of Eosinopteryx brevipenna. The authors used a modified version of the matrix from the study describing Xiaotingia, adding Jinfengopteryx elegans and Eosinopteryx brevipenna to it, as well as adding four additional characters related to the development of the plumage. Unlike the analysis from the description of Xiaotingia, the analysis conducted by Godefroit, et al. did not find Archaeopteryx to be related particularly closely to Anchiornis and Xiaotingia, which were recovered as basal troodontids instead. | Archaeopteryx | Wikipedia | 391 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Agnolín and Novas (2013) found Archaeopteryx and (possibly synonymous) Wellnhoferia to be from a clade sister to the lineage including Jeholornis and Pygostylia, with Microraptoria, Unenlagiinae, and the clade containing Anchiornis and Xiaotingia being successively closer outgroups to the Avialae (defined by the authors as the clade stemming from the last common ancestor of Archaeopteryx and Aves). Another phylogenetic study by Godefroit, et al., using a more inclusive matrix than the one from the analysis in the description of Eosinopteryx brevipenna, also found Archaeopteryx to be a member of Avialae (defined by the authors as the most inclusive clade containing Passer domesticus, but not Dromaeosaurus albertensis or Troodon formosus). Archaeopteryx was found to form a grade at the base of Avialae with Xiaotingia, Anchiornis, and Aurornis. Compared to Archaeopteryx, Xiaotingia was found to be more closely related to extant birds, while both Anchiornis and Aurornis were found to be more distantly so.
Hu et al. (2018), Wang et al. (2018) and Hartman et al. (2019) found Archaeopteryx to have been a deinonychosaur instead of an avialan. More specifically, it and closely related taxa were considered basal deinonychosaurs, with dromaeosaurids and troodontids forming together a parallel lineage within the group. Because Hartman et al. found Archaeopteryx isolated in a group of flightless deinonychosaurs (otherwise considered "anchiornithids"), they considered it highly probable that this animal evolved flight independently from bird ancestors (and from Microraptor and Yi). The following cladogram illustrates their hypothesis regarding the position of Archaeopteryx:
The authors, however, found that the Archaeopteryx being an avialan was only slightly less likely than this hypothesis, and as likely as Archaeopterygidae and Troodontidae being sister clades.
Palaeobiology
Flight | Archaeopteryx | Wikipedia | 478 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
As in the wings of modern birds, the flight feathers of Archaeopteryx were somewhat asymmetrical and the tail feathers were rather broad. This implies that the wings and tail were used for lift generation, but it is unclear whether Archaeopteryx was capable of flapping flight or simply a glider. The lack of a bony breastbone suggests that Archaeopteryx was not a very strong flier, but flight muscles might have attached to the thick, boomerang-shaped wishbone, the platelike coracoids, or perhaps, to a cartilaginous sternum. The sideways orientation of the glenoid (shoulder) joint between scapula, coracoid, and humerus—instead of the dorsally angled arrangement found in modern birds—may indicate that Archaeopteryx was unable to lift its wings above its back, a requirement for the upstroke found in modern flapping flight. According to a study by Philip Senter in 2006, Archaeopteryx was indeed unable to use flapping flight as modern birds do, but it may well have used a downstroke-only flap-assisted gliding technique. However, a more recent study solves this issue by suggesting a different flight stroke configuration for non-avian flying theropods.
Archaeopteryx wings were relatively large, which would have resulted in a low stall speed and reduced turning radius. The short and rounded shape of the wings would have increased drag, but also could have improved its ability to fly through cluttered environments such as trees and brush (similar wing shapes are seen in birds that fly through trees and brush, such as crows and pheasants). The presence of "hind wings", asymmetrical flight feathers stemming from the legs similar to those seen in dromaeosaurids such as Microraptor, also would have added to the aerial mobility of Archaeopteryx. The first detailed study of the hind wings by Longrich in 2006, suggested that the structures formed up to 12% of the total airfoil. This would have reduced stall speed by up to 6% and turning radius by up to 12%. | Archaeopteryx | Wikipedia | 446 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The feathers of Archaeopteryx were asymmetrical. This has been interpreted as evidence that it was a flyer, because flightless birds tend to have symmetrical feathers. Some scientists, including Thomson and Speakman, have questioned this. They studied more than 70 families of living birds, and found that some flightless types do have a range of asymmetry in their feathers, and that the feathers of Archaeopteryx fall into this range. The degree of asymmetry seen in Archaeopteryx is more typical for slow flyers than for flightless birds. | Archaeopteryx | Wikipedia | 118 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
In 2010, Robert L. Nudds and Gareth J. Dyke in the journal Science published a paper in which they analysed the rachises of the primary feathers of Confuciusornis and Archaeopteryx. The analysis suggested that the rachises on these two genera were thinner and weaker than those of modern birds relative to body mass. The authors determined that Archaeopteryx and Confuciusornis, were unable to use flapping flight. This study was criticized by Philip J. Currie and Luis Chiappe. Chiappe suggested that it is difficult to measure the rachises of fossilized feathers, and Currie speculated that Archaeopteryx and Confuciusornis must have been able to fly to some degree, as their fossils are preserved in what is believed to have been marine or lake sediments, suggesting that they must have been able to fly over deep water. Gregory Paul also disagreed with the study, arguing in a 2010 response that Nudds and Dyke had overestimated the masses of these early birds, and that more accurate mass estimates allowed powered flight even with relatively narrow rachises. Nudds and Dyke had assumed a mass of for the Munich specimen Archaeopteryx, a young juvenile, based on published mass estimates of larger specimens. Paul argued that a more reasonable body mass estimate for the Munich specimen is about . Paul also criticized the measurements of the rachises themselves, noting that the feathers in the Munich specimen are poorly preserved. Nudds and Dyke reported a diameter of for the longest primary feather, which Paul could not confirm using photographs. Paul measured some of the inner primary feathers, finding rachises across. Despite these criticisms, Nudds and Dyke stood by their original conclusions. They claimed that Paul's statement, that an adult Archaeopteryx would have been a better flyer than the juvenile Munich specimen, was dubious. This, they reasoned, would require an even thicker rachis, evidence for which has not yet been presented. Another possibility is that they had not achieved true flight, but instead used their wings as aids for extra lift while running over water after the fashion of the basilisk lizard, which could explain their presence in lake and marine deposits (see Origin of avian flight). | Archaeopteryx | Wikipedia | 467 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
In 2004, scientists analysing a detailed CT scan of the braincase of the London Archaeopteryx concluded that its brain was significantly larger than that of most dinosaurs, indicating that it possessed the brain size necessary for flying. The overall brain anatomy was reconstructed using the scan. The reconstruction showed that the regions associated with vision took up nearly one-third of the brain. Other well-developed areas involved hearing and muscle coordination. The skull scan also revealed the structure of its inner ear. The structure more closely resembles that of modern birds than the inner ear of non-avian reptiles. These characteristics taken together suggest that Archaeopteryx had the keen sense of hearing, balance, spatial perception, and coordination needed to fly. Archaeopteryx had a cerebrum-to-brain-volume ratio 78% of the way to modern birds from the condition of non-coelurosaurian dinosaurs such as Carcharodontosaurus or Allosaurus, which had a crocodile-like anatomy of the brain and inner ear. Newer research shows that while the Archaeopteryx brain was more complex than that of more primitive theropods, it had a more generalized brain volume among Maniraptora dinosaurs, even smaller than that of other non-avian dinosaurs in several instances, which indicates the neurological development required for flight was already a common trait in the maniraptoran clade.
Recent studies of flight feather barb geometry reveal that modern birds possess a larger barb angle in the trailing vane of the feather, whereas Archaeopteryx lacks this large barb angle, indicating potentially weak flight abilities. | Archaeopteryx | Wikipedia | 330 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
Archaeopteryx continues to play an important part in scientific debates about the origin and evolution of birds. Some scientists see it as a semi-arboreal climbing animal, following the idea that birds evolved from tree-dwelling gliders (the "trees down" hypothesis for the evolution of flight proposed by O. C. Marsh). Other scientists see Archaeopteryx as running quickly along the ground, supporting the idea that birds evolved flight by running (the "ground up" hypothesis proposed by Samuel Wendell Williston). Still others suggest that Archaeopteryx might have been at home both in the trees and on the ground, like modern crows, and this latter view is what currently is considered best supported by morphological characters. Altogether, it appears that the species was not particularly specialized for running on the ground or for perching. A scenario outlined by Elżanowski in 2002 suggested that Archaeopteryx used its wings mainly to escape predators by glides punctuated with shallow downstrokes to reach successively higher perches, and alternatively, to cover longer distances (mainly) by gliding down from cliffs or treetops.
In March 2018, scientists reported that Archaeopteryx was likely capable of a flight stroke cycle morphologically closer to the grabbing motion of maniraptorans and distinct from that of modern birds. This study on Archaeopteryxs bone histology identified biomechanical and physiological adaptations exhibited by modern volant birds that perform intermittent flapping, such as pheasants and other burst flyers.
Some researchers suggested that the feather sheaths of Archaeopteryx shows a center-out, flight related moulting strategy like modern birds. As it was a weak flier, this would have been extremely advantageous in preserving its maximum flight performance. Kiat and colleagues reinterpreted this purported moulting evidence to be problematic and equivocal at best, and considered that these structures more likely represents the calami traces of the fully grown feathers, though the original authors still remained by their conclusion.
Growth | Archaeopteryx | Wikipedia | 419 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
An histological study by Erickson, Norell, Zhongue, and others in 2009 estimated that Archaeopteryx grew relatively slowly compared to modern birds, presumably because the outermost portions of Archaeopteryx bones appear poorly vascularized; in living vertebrates, poorly vascularized bone is correlated with slow growth rate. They also assume that all known skeletons of Archaeopteryx come from juvenile specimens. Because the bones of Archaeopteryx could not be histologically sectioned in a formal skeletochronological (growth ring) analysis, Erickson and colleagues used bone vascularity (porosity) to estimate bone growth rate. They assumed that poorly vascularized bone grows at similar rates in all birds and in Archaeopteryx. The poorly vascularized bone of Archaeopteryx might have grown as slowly as that in a mallard (2.5micrometres per day) or as fast as that in an ostrich (4.2micrometres per day). Using this range of bone growth rates, they calculated how long it would take to "grow" each specimen of Archaeopteryx to the observed size; it may have taken at least 970 days (there were 375 days in a Late Jurassic year) to reach an adult size of . The study also found that the avialans Jeholornis and Sapeornis grew relatively slowly, as did the dromaeosaurid Mahakala. The avialans Confuciusornis and Ichthyornis grew relatively quickly, following a growth trend similar to that of modern birds. One of the few modern birds that exhibit slow growth is the flightless kiwi, and the authors speculated that Archaeopteryx and the kiwi had similar basal metabolic rate.
Daily activity patterns
Comparisons between the scleral rings of Archaeopteryx and modern birds and reptiles indicate that it may have been diurnal, similar to most modern birds.
Palaeoecology | Archaeopteryx | Wikipedia | 415 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The richness and diversity of the Solnhofen limestones in which all specimens of Archaeopteryx have been found have shed light on an ancient Jurassic Bavaria strikingly different from the present day. The latitude was similar to Florida, though the climate was likely to have been drier, as evidenced by fossils of plants with adaptations for arid conditions and a lack of terrestrial sediments characteristic of rivers. Evidence of plants, although scarce, include cycads and conifers while animals found include a large number of insects, small lizards, pterosaurs, and Compsognathus.
The excellent preservation of Archaeopteryx fossils and other terrestrial fossils found at Solnhofen indicates that they did not travel far before becoming preserved. The Archaeopteryx specimens found were therefore likely to have lived on the low islands surrounding the Solnhofen lagoon rather than to have been corpses that drifted in from farther away. Archaeopteryx skeletons are considerably less numerous in the deposits of Solnhofen than those of pterosaurs, of which seven genera have been found. The pterosaurs included species such as Rhamphorhynchus belonging to the Rhamphorhynchidae, the group which dominated the ecological niche currently occupied by seabirds, and which became extinct at the end of the Jurassic. The pterosaurs, which also included Pterodactylus, were common enough that it is unlikely that the specimens found are vagrants from the larger islands to the north.
The islands that surrounded the Solnhofen lagoon were low lying, semi-arid, and sub-tropical with a long dry season and little rain. The closest modern analogue for the Solnhofen conditions is said to be Orca Basin in the northern Gulf of Mexico, although it is much deeper than the Solnhofen lagoons. The flora of these islands was adapted to these dry conditions and consisted mostly of low () shrubs. Contrary to reconstructions of Archaeopteryx climbing large trees, these seem to have been mostly absent from the islands; few trunks have been found in the sediments and fossilized tree pollen also is absent. | Archaeopteryx | Wikipedia | 444 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
The lifestyle of Archaeopteryx is difficult to reconstruct and there are several theories regarding it. Some researchers suggest that it was primarily adapted to life on the ground, while other researchers suggest that it was principally arboreal on the basis of the curvature of the claws which has since been questioned. The absence of trees does not preclude Archaeopteryx from an arboreal lifestyle, as several species of bird live exclusively in low shrubs. Various aspects of the morphology of Archaeopteryx point to either an arboreal or ground existence, including the length of its legs and the elongation in its feet; some authorities consider it likely to have been a generalist capable of feeding in both shrubs and open ground, as well as along the shores of the lagoon. It most likely hunted small prey, seizing it with its jaws if it was small enough, or with its claws if it was larger. | Archaeopteryx | Wikipedia | 186 | 2995 | https://en.wikipedia.org/wiki/Archaeopteryx | Biology and health sciences | General articles | null |
In chemistry, an acid–base reaction is a chemical reaction that occurs between an acid and a base. It can be used to determine pH via titration. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory.
Their importance becomes apparent in analyzing acid–base reactions for gaseous or liquid species, or when acid or base character may be somewhat less apparent. The first of these concepts was provided by the French chemist Antoine Lavoisier, around 1776.
It is important to think of the acid–base reaction models as theories that complement each other. For example, the current Lewis model has the broadest definition of what an acid and base are, with the Brønsted–Lowry theory being a subset of what acids and bases are, and the Arrhenius theory being the most restrictive.
Acid–base definitions
Historic development
The concept of an acid–base reaction was first proposed in 1754 by Guillaume-François Rouelle, who introduced the word "base" into chemistry to mean a substance which reacts with an acid to give it solid form (as a salt). Bases are mostly bitter in nature. | Acid–base reaction | Wikipedia | 258 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Lavoisier's oxygen theory of acids
The first scientific concept of acids and bases was provided by Lavoisier in around 1776. Since Lavoisier's knowledge of strong acids was mainly restricted to oxoacids, such as (nitric acid) and (sulfuric acid), which tend to contain central atoms in high oxidation states surrounded by oxygen, and since he was not aware of the true composition of the hydrohalic acids (HF, HCl, HBr, and HI), he defined acids in terms of their containing oxygen, which in fact he named from Greek words meaning "acid-former" (). The Lavoisier definition held for over 30 years, until the 1810 article and subsequent lectures by Sir Humphry Davy in which he proved the lack of oxygen in hydrogen sulfide (), hydrogen telluride (), and the hydrohalic acids. However, Davy failed to develop a new theory, concluding that "acidity does not depend upon any particular elementary substance, but upon peculiar arrangement of various substances". One notable modification of oxygen theory was provided by Jöns Jacob Berzelius, who stated that acids are oxides of nonmetals while bases are oxides of metals.
Liebig's hydrogen theory of acids
In 1838, Justus von Liebig proposed that an acid is a hydrogen-containing compound whose hydrogen can be replaced by a metal. This redefinition was based on his extensive work on the chemical composition of organic acids, finishing the doctrinal shift from oxygen-based acids to hydrogen-based acids started by Davy. Liebig's definition, while completely empirical, remained in use for almost 50 years until the adoption of the Arrhenius definition.
Arrhenius definition
The first modern definition of acids and bases in molecular terms was devised by Svante Arrhenius. A hydrogen theory of acids, it followed from his 1884 work with Friedrich Wilhelm Ostwald in establishing the presence of ions in aqueous solution and led to Arrhenius receiving the Nobel Prize in Chemistry in 1903.
As defined by Arrhenius:
An Arrhenius acid is a substance that ionises in water to form hydrogen ions (); that is, an acid increases the concentration of H+ ions in an aqueous solution. | Acid–base reaction | Wikipedia | 481 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
This causes the protonation of water, or the creation of the hydronium () ion. Thus, in modern times, the symbol is interpreted as a shorthand for , because it is now known that a bare proton does not exist as a free species in aqueous solution. This is the species which is measured by pH indicators to measure the acidity or basicity of a solution.
An Arrhenius base is a substance that dissociates in water to form hydroxide () ions; that is, a base increases the concentration of ions in an aqueous solution.
The Arrhenius definitions of acidity and alkalinity are restricted to aqueous solutions and are not valid for most non-aqueous solutions, and refer to the concentration of the solvent ions. Under this definition, pure and HCl dissolved in toluene are not acidic, and molten NaOH and solutions of calcium amide in liquid ammonia are not alkaline. This led to the development of the Brønsted–Lowry theory and subsequent Lewis theory to account for these non-aqueous exceptions.
The reaction of an acid with a base is called a neutralization reaction. The products of this reaction are a salt and water.
In this traditional representation an acid–base neutralization reaction is formulated as a double-replacement reaction. For example, the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH) solutions produces a solution of sodium chloride (NaCl) and some additional water molecules.
The modifier (aq) in this equation was implied by Arrhenius, rather than included explicitly. It indicates that the substances are dissolved in water. Though all three substances, HCl, NaOH and NaCl are capable of existing as pure compounds, in aqueous solutions they are fully dissociated into the aquated ions and .
Example: Baking powder
Baking powder is used to cause the dough for breads and cakes to "rise" by creating millions of tiny carbon dioxide bubbles. Baking powder is not to be confused with baking soda, which is sodium bicarbonate (). Baking powder is a mixture of baking soda (sodium bicarbonate) and acidic salts. The bubbles are created because, when the baking powder is combined with water, the sodium bicarbonate and acid salts react to produce gaseous carbon dioxide. | Acid–base reaction | Wikipedia | 486 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Whether commercially or domestically prepared, the principles behind baking powder formulations remain the same. The acid–base reaction can be generically represented as shown:
The real reactions are more complicated because the acids are complicated. For example, starting with sodium bicarbonate and monocalcium phosphate (), the reaction produces carbon dioxide by the following stoichiometry:
A typical formulation (by weight) could call for 30% sodium bicarbonate, 5–12% monocalcium phosphate, and 21–26% sodium aluminium sulfate. Alternately, a commercial baking powder might use sodium acid pyrophosphate as one of the two acidic components instead of sodium aluminium sulfate. Another typical acid in such formulations is cream of tartar (), a derivative of tartaric acid.
Brønsted–Lowry definition
The Brønsted–Lowry definition, formulated in 1923, independently by Johannes Nicolaus Brønsted in Denmark and Martin Lowry in England, is based upon the idea of protonation of bases through the deprotonation of acids – that is, the ability of acids to "donate" hydrogen ions () otherwise known as protons to bases, which "accept" them.
An acid–base reaction is, thus, the removal of a hydrogen ion from the acid and its addition to the base. The removal of a hydrogen ion from an acid produces its conjugate base, which is the acid with a hydrogen ion removed. The reception of a proton by a base produces its conjugate acid, which is the base with a hydrogen ion added. | Acid–base reaction | Wikipedia | 322 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Unlike the previous definitions, the Brønsted–Lowry definition does not refer to the formation of salt and solvent, but instead to the formation of conjugate acids and conjugate bases, produced by the transfer of a proton from the acid to the base. In this approach, acids and bases are fundamentally different in behavior from salts, which are seen as electrolytes, subject to the theories of Debye, Onsager, and others. An acid and a base react not to produce a salt and a solvent, but to form a new acid and a new base. The concept of neutralization is thus absent. Brønsted–Lowry acid–base behavior is formally independent of any solvent, making it more all-encompassing than the Arrhenius model. The calculation of pH under the Arrhenius model depended on alkalis (bases) dissolving in water (aqueous solution). The Brønsted–Lowry model expanded what could be pH tested using insoluble and soluble solutions (gas, liquid, solid).
The general formula for acid–base reactions according to the Brønsted–Lowry definition is:
where HA represents the acid, B represents the base, represents the conjugate acid of B, and represents the conjugate base of HA.
For example, a Brønsted–Lowry model for the dissociation of hydrochloric acid (HCl) in aqueous solution would be the following:
The removal of from the produces the chloride ion, , the conjugate base of the acid. The addition of to the (acting as a base) forms the hydronium ion, , the conjugate acid of the base.
Water is amphoteric that is, it can act as both an acid and a base. The Brønsted–Lowry model explains this, showing the dissociation of water into low concentrations of hydronium and hydroxide ions:
This equation is demonstrated in the image below:
Here, one molecule of water acts as an acid, donating an and forming the conjugate base, , and a second molecule of water acts as a base, accepting the ion and forming the conjugate acid, .
As an example of water acting as an acid, consider an aqueous solution of pyridine, .
In this example, a water molecule is split into a hydrogen ion, which is donated to a pyridine molecule, and a hydroxide ion. | Acid–base reaction | Wikipedia | 510 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
In the Brønsted–Lowry model, the solvent does not necessarily have to be water, as is required by the Arrhenius Acid–Base model. For example, consider what happens when acetic acid, , dissolves in liquid ammonia.
An ion is removed from acetic acid, forming its conjugate base, the acetate ion, . The addition of an ion to an ammonia molecule of the solvent creates its conjugate acid, the ammonium ion, .
The Brønsted–Lowry model calls hydrogen-containing substances (like ) acids. Thus, some substances, which many chemists considered to be acids, such as or , are excluded from this classification due to lack of hydrogen. Gilbert N. Lewis wrote in 1938, "To restrict the group of acids to those substances that contain hydrogen interferes as seriously with the systematic understanding of chemistry as would the restriction of the term oxidizing agent to substances containing oxygen." Furthermore, and are not considered Brønsted bases, but rather salts containing the bases and .
Lewis definition
The hydrogen requirement of Arrhenius and Brønsted–Lowry was removed by the Lewis definition of acid–base reactions, devised by Gilbert N. Lewis in 1923, in the same year as Brønsted–Lowry, but it was not elaborated by him until 1938. Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a Lewis base) to be a compound that can donate an electron pair, and an acid (a Lewis acid) to be a compound that can receive this electron pair.
For example, boron trifluoride, is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet. The fluoride ion has a full octet and can donate a pair of electrons. Thus | Acid–base reaction | Wikipedia | 387 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
is a typical Lewis acid, Lewis base reaction. All compounds of group 13 elements with a formula can behave as Lewis acids. Similarly, compounds of group 15 elements with a formula , such as amines, , and phosphines, , can behave as Lewis bases. Adducts between them have the formula with a dative covalent bond, shown symbolically as ←, between the atoms A (acceptor) and D (donor). Compounds of group 16 with a formula may also act as Lewis bases; in this way, a compound like an ether, , or a thioether, , can act as a Lewis base. The Lewis definition is not limited to these examples. For instance, carbon monoxide acts as a Lewis base when it forms an adduct with boron trifluoride, of formula .
Adducts involving metal ions are referred to as co-ordination compounds; each ligand donates a pair of electrons to the metal ion. The reaction
can be seen as an acid–base reaction in which a stronger base (ammonia) replaces a weaker one (water).
The Lewis and Brønsted–Lowry definitions are consistent with each other since the reaction
is an acid–base reaction in both theories.
Solvent system definition
One of the limitations of the Arrhenius definition is its reliance on water solutions. Edward Curtis Franklin studied the acid–base reactions in liquid ammonia in 1905 and pointed out the similarities to the water-based Arrhenius theory. Albert F.O. Germann, working with liquid phosgene, , formulated the solvent-based theory in 1925, thereby generalizing the Arrhenius definition to cover aprotic solvents.
Germann pointed out that in many solutions, there are ions in equilibrium with the neutral solvent molecules:
solvonium ions: a generic name for positive ions. These are also sometimes called solvo-acids; when protonated solvent, they are lyonium ions.
solvate ions: a generic name for negative ions. These are also sometimes called solve-bases; when deprotonated solvent, they are lyate ions.
For example, water and ammonia undergo such dissociation into hydronium and hydroxide, and ammonium and amide, respectively: | Acid–base reaction | Wikipedia | 460 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Some aprotic systems also undergo such dissociation, such as dinitrogen tetroxide into nitrosonium and nitrate, antimony trichloride into dichloroantimonium and tetrachloroantimonate, and phosgene into chlorocarboxonium and chloride:
A solute that causes an increase in the concentration of the solvonium ions and a decrease in the concentration of solvate ions is defined as an acid. A solute that causes an increase in the concentration of the solvate ions and a decrease in the concentration of the solvonium ions is defined as a base.
Thus, in liquid ammonia, (supplying ) is a strong base, and (supplying ) is a strong acid. In liquid sulfur dioxide (), thionyl compounds (supplying ) behave as acids, and sulfites (supplying ) behave as bases.
The non-aqueous acid–base reactions in liquid ammonia are similar to the reactions in water:
Nitric acid can be a base in liquid sulfuric acid:
The unique strength of this definition shows in describing the reactions in aprotic solvents; for example, in liquid :
Because the solvent system definition depends on the solute as well as on the solvent itself, a particular solute can be either an acid or a base depending on the choice of the solvent: is a strong acid in water, a weak acid in acetic acid, and a weak base in fluorosulfonic acid; this characteristic of the theory has been seen as both a strength and a weakness, because some substances (such as and ) have been seen to be acidic or basic on their own right. On the other hand, solvent system theory has been criticized as being too general to be useful. Also, it has been thought that there is something intrinsically acidic about hydrogen compounds, a property not shared by non-hydrogenic solvonium salts.
Lux–Flood definition
This acid–base theory was a revival of the oxygen theory of acids and bases proposed by German chemist Hermann Lux in 1939, further improved by Håkon Flood and is still used in modern geochemistry and electrochemistry of molten salts. This definition describes an acid as an oxide ion () acceptor and a base as an oxide ion donor. For example:
This theory is also useful in the systematisation of the reactions of noble gas compounds, especially the xenon oxides, fluorides, and oxofluorides. | Acid–base reaction | Wikipedia | 506 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Usanovich definition
Mikhail Usanovich developed a general theory that does not restrict acidity to hydrogen-containing compounds, but his approach, published in 1938, was even more general than Lewis theory. Usanovich's theory can be summarized as defining an acid as anything that accepts negative species or donates positive ones, and a base as the reverse. This defined the concept of redox (oxidation-reduction) as a special case of acid–base reactions.
Some examples of Usanovich acid–base reactions include:
Rationalizing the strength of Lewis acid–base interactions
HSAB theory
In 1963, Ralph Pearson proposed a qualitative concept known as the Hard and Soft Acids and Bases principle. later made quantitative with help of Robert Parr in 1984. 'Hard' applies to species that are small, have high charge states, and are weakly polarizable. 'Soft' applies to species that are large, have low charge states and are strongly polarizable. Acids and bases interact, and the most stable interactions are hard–hard and soft–soft. This theory has found use in organic and inorganic chemistry.
ECW model
The ECW model created by Russell S. Drago is a quantitative model that describes and predicts the strength of Lewis acid base interactions, . The model assigned and parameters to many Lewis acids and bases. Each acid is characterized by an and a . Each base is likewise characterized by its own and . The and parameters refer, respectively, to the electrostatic and covalent contributions to the strength of the bonds that the acid and base will form. The equation is
The term represents a constant energy contribution for acid–base reaction such as the cleavage of a dimeric acid or base. The equation predicts reversal of acids and base strengths. The graphical presentations of the equation show that there is no single order of Lewis base strengths or Lewis acid strengths.
Acid–base equilibrium
The reaction of a strong acid with a strong base is essentially a quantitative reaction. For example,
In this reaction both the sodium and chloride ions are spectators as the neutralization reaction,
does not involve them. With weak bases addition of acid is not quantitative because a solution of a weak base is a buffer solution. A solution of a weak acid is also a buffer solution. When a weak acid reacts with a weak base an equilibrium mixture is produced. For example, adenine, written as AH, can react with a hydrogen phosphate ion, . | Acid–base reaction | Wikipedia | 490 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
The equilibrium constant for this reaction can be derived from the acid dissociation constants of adenine and of the dihydrogen phosphate ion.
The notation [X] signifies "concentration of X". When these two equations are combined by eliminating the hydrogen ion concentration, an expression for the equilibrium constant, is obtained.
Acid–alkali reaction
An acid–alkali reaction is a special case of an acid–base reaction, where the base used is also an alkali. When an acid reacts with an alkali salt (a metal hydroxide), the product is a metal salt and water. Acid–alkali reactions are also neutralization reactions.
In general, acid–alkali reactions can be simplified to
by omitting spectator ions.
Acids are in general pure substances that contain hydrogen cations () or cause them to be produced in solutions. Hydrochloric acid () and sulfuric acid () are common examples. In water, these break apart into ions:
The alkali breaks apart in water, yielding dissolved hydroxide ions:
. | Acid–base reaction | Wikipedia | 215 | 3038 | https://en.wikipedia.org/wiki/Acid%E2%80%93base%20reaction | Physical sciences | Chemistry | null |
Autumn, also known as fall, is one of the four temperate seasons on Earth. Outside the tropics, autumn marks the transition from summer to winter, in September (Northern Hemisphere) or March (Southern Hemisphere). Autumn is the season when the duration of daylight becomes noticeably shorter and the temperature cools considerably. Day length decreases and night length increases as the season progresses until the winter solstice in December (Northern Hemisphere) and June (Southern Hemisphere). One of its main features in temperate climates is the striking change in colour of the leaves of deciduous trees as they prepare to shed.
Date definitions
Some cultures regard the autumnal equinox as "mid-autumn", while others with a longer temperature lag treat the equinox as the start of autumn. In the English-speaking world of high latitude countries, autumn traditionally began with Lammas Day and ended around Hallowe'en, the approximate mid-points between midsummer, the autumnal equinox, and midwinter. Meteorologists (and Australia and most of the temperate countries in the southern hemisphere) use a definition based on Gregorian calendar months, with autumn being September, October, and November in the northern hemisphere, and March, April, and May in the southern hemisphere.
In the higher latitude countries in the Northern Hemisphere, autumn traditionally starts with the September equinox (21 to 24 September) and ends with the winter solstice (21 or 22 December). Popular culture in the United States associates Labor Day, the first Monday in September, as the end of summer and the start of autumn. Certain summer traditions, such as wearing white, are discouraged after that date. As daytime and nighttime temperatures decrease, trees change colour and then shed their leaves. Persians celebrate the beginning of the autumn on Mehregan. | Autumn | Wikipedia | 364 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
Under the traditional East Asian solar term system, autumn starts on or around 8 August and ends on or about 7 November. In Ireland, the autumn months according to the national meteorological service, Met Éireann, are September, October, and November. However, according to the Irish Calendar, which is based on ancient Gaelic traditions, autumn lasts throughout the months of August, September, and October, or possibly a few days later, depending on tradition. In the Irish language, September is known as ("middle of autumn") and October as ("end of autumn"). Late Roman Republic scholar Marcus Terentius Varro defined autumn as lasting from the third day before the Ides of Sextilis (August 11) to the fifth day before the Ides of November (November 9).
Etymology
The word autumn () is derived from Latin autumnus, archaic auctumnus, possibly from the ancient Etruscan root autu- and has within it connotations of the passing of the year. Alternative etymologies include ) or ('dry').
After the Greek era, the word continued to be used as the Old French word ( in modern French) or in Middle English, and was later normalised to the original Latin. In the Medieval period, there are rare examples of its use as early as the 12th century, but by the 16th century, it was in common use.
Before the 16th century, harvest was the term usually used to refer to the season, as it is common in other West Germanic languages to this day (cf. Dutch , German , and Scots ). However, as more people gradually moved from working the land to living in towns, the word harvest lost its reference to the time of year and came to refer only to the actual activity of reaping, and autumn, as well as fall, began to replace it as a reference to the season.
The alternative word fall for the season traces its origins to old Germanic languages. The exact derivation is unclear, with the Old English or and the Old Norse all being possible candidates. However, these words all have the meaning "to fall from a height" and are clearly derived either from a common root or from each other. The term came to denote the season in 16th-century England, a contraction of Middle English expressions like "fall of the leaf" and "fall of the year". Compare the origin of spring from "spring of the leaf" and "spring of the year". | Autumn | Wikipedia | 501 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
During the 17th century, English settlers began emigrating to the new North American colonies, and took the English language with them. While the term fall gradually became nearly obsolete in Britain, it became the more common term in North America.
The name backend, a once common name for the season in Northern England, has today been largely replaced by the name autumn.
Associations
Harvest
Association with the transition from warm to cold weather, and its related status as the season of the primary harvest, has dominated its themes and popular images. In Western cultures, personifications of autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Many cultures feature autumnal harvest festivals, often the most important on their calendars.
Still-extant echoes of these celebrations are found in the autumn Thanksgiving holiday of the United States and Canada, and the Jewish Sukkot holiday with its roots as a full-moon harvest festival of "tabernacles" (living in outdoor huts around the time of harvest). There are also the many festivals celebrated by indigenous peoples of the Americas tied to the harvest of ripe foods gathered in the wild, the Chinese Mid-Autumn or Moon festival, and many others. The predominant mood of these autumnal celebrations is a gladness for the fruits of the earth mixed with a certain melancholy linked to the imminent arrival of harsh weather.
This view is presented in English poet John Keats' poem To Autumn, where he describes the season as a time of bounteous fecundity, a time of "mellow fruitfulness".
In North America, while most foods are harvested during the autumn, foods usually associated with the season include pumpkins (which are integral parts of both Thanksgiving and Halloween) and apples, which are used to make the seasonal beverage apple cider.
Melancholia
Autumn, especially in poetry, has often been associated with melancholia. The possibilities and opportunities of summer are gone, and the chill of winter is on the horizon. Skies turn grey, the amount of usable daylight drops rapidly, and many people turn inward, both physically and mentally. It has been referred to as an unhealthy season. | Autumn | Wikipedia | 444 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
Similar examples may be found in Irish poet W.B. Yeats' poem The Wild Swans at Coole where the maturing season that the poet observes symbolically represents his own ageing self. Like the natural world that he observes, he too has reached his prime and now must look forward to the inevitability of old age and death. French poet Paul Verlaine's "Chanson d'automne" ("Autumn Song") is likewise characterised by strong, painful feelings of sorrow. Keats' To Autumn, written in September 1819, echoes this sense of melancholic reflection but also emphasises the lush abundance of the season. The song "Autumn Leaves", based on the French song "Les Feuilles mortes", uses the melancholic atmosphere of the season and the end of summer as a metaphor for the mood of being separated from a loved one.
Halloween
Autumn is associated with Halloween (influenced by Samhain, a Celtic autumn festival), and with it a widespread marketing campaign that promotes it. The Celtic people also used this time to celebrate the harvest with a time of feasting. At the same time though, it was a celebration of death as well. Crops were harvested, livestock were butchered, and Winter was coming.
Halloween, 31 October, is in autumn in the northern hemisphere. Television, film, book, costume, home decoration, and confectionery businesses use this time of year to promote products closely associated with such a holiday, with promotions going from late August or early September to 31 October, since their themes rapidly lose strength once the holiday ends, and advertising starts concentrating on Christmas.
Other associations
In some parts of the northern hemisphere, autumn has a strong association with the end of summer holiday and the start of a new school year, particularly for children in primary and secondary education. "Back to School" advertising and preparations usually occurs in the weeks leading to the beginning of autumn.
Thanksgiving Day is a national holiday celebrated in Canada, in the United States, in some of the Caribbean islands and in Liberia. Thanksgiving is celebrated on the second Monday of October in Canada, on the fourth Thursday of November in the United States (where it is commonly regarded as the start of the Christmas and holiday season), and around the same part of the year in other places. Similarly named festival holidays occur in Germany and Japan. | Autumn | Wikipedia | 484 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
Television stations and networks, particularly in North America, traditionally begin their regular seasons in their autumn, with new series and new episodes of existing series debuting mostly during late September or early October (series that debut outside the autumn season are usually known as mid-season replacements). A sweeps period takes place in November to measure Nielsen Ratings.
American football is played almost exclusively in the autumn months; at the high school level, seasons run from late August through early November, with some playoff games and holiday rivalry contests being played as late as Thanksgiving. In many American states, the championship games take place in early December. College football's regular season runs from September through November, while the main professional circuit, the National Football League, plays from September through to early January.
Summer sports, such as association football (in Northern America, East Asia, Argentina, and South Africa), Canadian football, stock car racing, tennis, golf, cricket, and professional baseball, wrap up their seasons in early to late autumn; Major League Baseball's championship World Series is popularly known as the "Fall Classic". (Amateur baseball is usually finished by August.) Likewise, professional winter sports, such as ice hockey and basketball, and most leagues of association football in Europe, are in the early stages of their seasons during autumn; American college basketball and college ice hockey play teams outside their athletic conferences during the late autumn before their in-conference schedules begin in winter.
The Christian religious holidays of All Saints' Day and All Souls' Day are observed in autumn in the Northern hemisphere. Easter falls in autumn in the southern hemisphere.
The secular celebration of International Workers' Day also falls in autumn in the southern hemisphere.
Since 1997, Autumn has been one of the top 100 names for girls in the United States.
In Indian mythology, autumn is considered to be the preferred season for the goddess of learning Saraswati, who is also known by the name of "goddess of autumn" (Sharada).
In Asian mysticism, Autumn is associated with the element of metal, and subsequently with the colour white, the White Tiger of the West, and death and mourning.
Tourism
Although colour change in leaves occurs wherever deciduous trees are found, coloured autumn foliage is noted in various regions of the world: most of North America, Eastern Asia (including China, Korea, and Japan), Europe, southeast, south, and part of the midwest of Brazil, the forest of Patagonia, eastern Australia and New Zealand's South Island. | Autumn | Wikipedia | 502 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
Eastern Canada and New England are famous for their autumnal foliage, and this attracts major tourism (worth billions of US dollars) for the regions.
Views of autumn
Allegories of autumn in art | Autumn | Wikipedia | 39 | 3049 | https://en.wikipedia.org/wiki/Autumn | Physical sciences | Seasons | null |
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Arcturus is the brightest star in the northern constellation of Boötes. With an apparent visual magnitude of −0.05, it is the fourth-brightest star in the night sky, and the brightest in the northern celestial hemisphere. The name Arcturus originated from ancient Greece; it was then cataloged as α Boötis by Johann Bayer in 1603, which is Latinized to Alpha Boötis. Arcturus forms one corner of the Spring Triangle asterism.
Located relatively close at 36.7 light-years from the Sun, Arcturus is a red giant of spectral type K1.5III—an aging star around 7.1 billion years old that has used up its core hydrogen and evolved off the main sequence. It is about the same mass as the Sun, but has expanded to 25 times its size (around 35 million kilometers) and is around 170 times as luminous.
Nomenclature
The traditional name Arcturus is Latinised from the ancient Greek Ἀρκτοῦρος (Arktouros) and means "Guardian of the Bear", ultimately from ἄρκτος (arktos), "bear" and οὖρος (ouros), "watcher, guardian".
The designation of Arcturus as α Boötis (Latinised to Alpha Boötis) was made by Johann Bayer in 1603. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Arcturus for α Boötis.
Observation | Arcturus | Wikipedia | 372 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27). However, α Centauri AB is a binary star, whose components are each fainter than Arcturus. This makes Arcturus the third-brightest individual star, just ahead of α Centauri A (officially named Rigil Kentaurus), whose apparent magnitude . The French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope in 1635. This was the first recorded full daylight viewing for any star other than the Sun and supernovae. Arcturus has been seen at or just before sunset with the naked eye.
Arcturus is visible from both of Earth's hemispheres as it is located 19° north of the celestial equator. The star culminates at midnight on 27 April, and at 9 p.m. on June 10 being visible during the late northern spring or the southern autumn. From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper (or Plough in the UK). By continuing in this path, one can find Spica, "Arc to Arcturus, then spike (or speed on) to Spica". Together with the bright stars Spica and Regulus (or Denebola, depending on the source), Arcturus is part of the Spring Triangle asterism. With Cor Caroli, these four stars form the Great Diamond asterism.
Ptolemy described Arcturus as subrufa ("slightly red"): it has a B-V color index of +1.23, roughly midway between Pollux (B-V +1.00) and Aldebaran (B-V +1.54).
η Boötis, or Muphrid, is only 3.3 light-years distant from Arcturus, and would have a visual magnitude −2.5, about as bright as Jupiter at its brightest from Earth, whereas an observer on the former system would find Arcturus with a magnitude -5.0, slightly brighter than Venus as seen from Earth, but with an orangish color.
Physical characteristics | Arcturus | Wikipedia | 502 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
Based upon an annual parallax shift of 88.83 milliarcseconds, as measured by the Hipparcos satellite, Arcturus is from Earth. The parallax margin of error is 0.54 milliarcseconds, translating to a distance margin of error of ±. Because of its proximity, Arcturus has a high proper motion, two arcseconds a year, greater than any first magnitude star other than α Centauri. It is [[list of nearest giant stars|the second-closest giant star to Earth, after Pollux.
Arcturus is moving rapidly () relative to the Sun, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. (In antiquity, Arcturus was closer to the centre of the constellation.) Arcturus is thought to be an old-disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.
With an absolute magnitude of −0.30, Arcturus is, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood. It is about 110 times brighter than the Sun in visible light wavelengths, but this underestimates its strength as much of the light it gives off is in the infrared; total (bolometric) power output is about 180 times that of the Sun. With a near-infrared J band magnitude of −2.2, only Betelgeuse (−2.9) and R Doradus (−2.6) are brighter. The lower output in visible light is due to a lower efficacy as the star has a lower surface temperature than the Sun. | Arcturus | Wikipedia | 380 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
There have been suggestions that Arcturus might be a member of a binary system with a faint, cool companion, but no companion has been directly detected.
In the absence of a binary companion, the mass of Arcturus cannot be measured directly, but models suggest it is slightly greater than that of the Sun. Evolutionary matching to the observed physical parameters gives a mass of , while the oxygen isotope ratio for a first dredge-up star gives a mass of . The star, given its evolutionary state, is expected to have undergone significant mass loss in the past. The star displays magnetic activity that is heating the coronal structures, and it undergoes a solar-type magnetic cycle with a duration that is probably less than 14 years. A weak magnetic field has been detected in the photosphere with a strength of around half a gauss. The magnetic activity appears to lie along four latitudes and is rotationally modulated.
Arcturus is estimated to be around 6 to 8.5 billion years old, but there is some uncertainty about its evolutionary status. Based upon the color characteristics of Arcturus, it is currently ascending the red-giant branch and will continue to do so until it accumulates a large enough degenerate helium core to ignite the helium flash. It has likely exhausted the hydrogen from its core and is now in its active hydrogen shell burning phase. However, Charbonnel et al. (1998) placed it slightly above the horizontal branch, and suggested it has already completed the helium flash stage.
Spectrum
Arcturus has evolved off the main sequence to the red giant branch, reaching an early K-type stellar classification. It is frequently assigned the spectral type of K0III, but in 1989 was used as the spectral standard for type K1.5III Fe−0.5, with the suffix notation indicating a mild underabundance of iron compared to typical stars of its type. As the brightest K-type giant in the sky, it has been the subject of multiple atlases with coverage from the ultraviolet to infrared. | Arcturus | Wikipedia | 414 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
The spectrum shows a dramatic transition from emission lines in the ultraviolet to atomic absorption lines in the visible range and molecular absorption lines in the infrared. This is due to the optical depth of the atmosphere varying with wavelength. The spectrum shows very strong absorption in some molecular lines that are not produced in the photosphere but in a surrounding shell. Examination of carbon monoxide lines show the molecular component of the atmosphere extending outward to 2–3 times the radius of the star, with the chromospheric wind steeply accelerating to 35–40 km/s in this region.
Astronomers term "metals" those elements with higher atomic numbers than helium. The atmosphere of Arcturus has an enrichment of alpha elements relative to iron but only about a third of solar metallicity. Arcturus is possibly a Population II star.
Oscillations
As one of the brightest stars in the sky, Arcturus has been the subject of a number of studies in the emerging field of asteroseismology. Belmonte and colleagues carried out a radial velocity (Doppler shift of spectral lines) study of the star in April and May 1988, which showed variability with a frequency of the order of a few microhertz (μHz), the highest peak corresponding to 4.3 μHz (2.7 days) with an amplitude of 60 ms−1, with a frequency separation of c. 5 μHz. They suggested that the most plausible explanation for the variability of Arcturus is stellar oscillations.
Asteroseismological measurements allow direct calculation of the mass and radius, giving values of and . This form of modelling is still relatively inaccurate, but a useful check on other models.
Search for planets
Hipparcos satellite astrometry suggested that Arcturus is a binary star, with the companion about twenty times dimmer than the primary and orbiting close enough to be at the very limits of humans' current ability to make it out. Recent results remain inconclusive, but do support the marginal Hipparcos detection of a binary companion. | Arcturus | Wikipedia | 416 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
In 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Arcturus exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. This substellar object would be nearly 12 times the mass of Jupiter and be located roughly at the same orbital distance from Arcturus as the Earth is from the Sun, at 1.1 astronomical units. However, all three stars surveyed showed similar oscillations yielding similar companion masses, and the authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion. So far no substellar companion has been confirmed.
Mythology
One astronomical tradition associates Arcturus with the mythology around Arcas, who was about to shoot and kill his own mother Callisto who had been transformed into a bear. Zeus averted their imminent tragic fate by transforming the boy into the constellation Boötes, called Arctophylax "bear guardian" by the Greeks, and his mother into Ursa Major (Greek: Arctos "the bear"). The account is given in Hyginus's Astronomy.
Aratus in his Phaenomena said that the star Arcturus lay below the belt of Arctophylax, and according to Ptolemy in the Almagest it lay between his thighs.
An alternative lore associates the name with the legend around Icarius, who gave the gift of wine to other men, but was murdered by them, because they had had no experience with intoxication and mistook the wine for poison. It is stated that Icarius became Arcturus while his dog, Maira, became Canicula (Procyon), although "Arcturus" here may be used in the sense of the constellation rather than the star.
Cultural significance
As one of the brightest stars in the sky, Arcturus has been significant to observers since antiquity.
In ancient Mesopotamia, it was linked to the god Enlil, and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. | Arcturus | Wikipedia | 448 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
In ancient Greek, the star is found in ancient astronomical literature, e.g. Hesiod's Work and Days, circa 700 BC, as well as Hipparchus's and Ptolemy's star catalogs. The folk-etymology connecting the star name with the bears (Greek: ἄρκτος, arktos) was probably invented much later. It fell out of use in favour of Arabic names until it was revived in the Renaissance. Arcturus is also mentioned in Plato's "Laws" (844e) as a herald for the season of vintage, specifically figs and grapes.
In Arabic, Arcturus is one of two stars called al-simāk "the uplifted ones" (the other is Spica). Arcturus is specified as السماك الرامح as-simāk ar-rāmiħ "the uplifted one of the lancer". The term Al Simak Al Ramih has appeared in Al Achsasi Al Mouakket catalogue (translated into Latin as Al Simak Lanceator). This has been variously romanized in the past, leading to obsolete variants such as Aramec and Azimech. For example, the name Alramih is used in Geoffrey Chaucer's A Treatise on the Astrolabe (1391). Another Arabic name is Haris-el-sema, from حارس السماء ħāris al-samā’ "the keeper of heaven". or حارس الشمال ħāris al-shamāl’ "the keeper of north".
In Indian astronomy, Arcturus is called Swati or Svati (Devanagari स्वाति, Transliteration IAST svāti, svātī́), possibly 'su' + 'ati' ("great goer", in reference to its remoteness) meaning very beneficent. It has been referred to as "the real pearl" in Bhartṛhari's kāvyas.
In Chinese astronomy, Arcturus is called Da Jiao (), because it is the brightest star in the Chinese constellation called Jiao Xiu (). Later it became a part of another constellation Kang Xiu (). | Arcturus | Wikipedia | 478 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
The Wotjobaluk Koori people of southeastern Australia knew Arcturus as Marpean-kurrk, mother of Djuit (Antares) and another star in Boötes, Weet-kurrk (Muphrid). Its appearance in the north signified the arrival of the larvae of the wood ant (a food item) in spring. The beginning of summer was marked by the star's setting with the Sun in the west and the disappearance of the larvae. The people of Milingimbi Island in Arnhem Land saw Arcturus and Muphrid as man and woman, and took the appearance of Arcturus at sunrise as a sign to go and harvest rakia or spikerush. The Weilwan of northern New South Wales knew Arcturus as Guembila "red".
Prehistoric Polynesian navigators knew Arcturus as Hōkūleʻa, the "Star of Joy". Arcturus is the zenith star of the Hawaiian Islands. Using Hōkūleʻa and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands. Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of the island chain, they sailed due west on the trade winds to landfall. If Hōkūleʻa could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaii. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the Polynesian Voyaging Society's Hōkūleʻa has crossed the Pacific Ocean many times under navigators who have incorporated this wayfinding technique in their non-instrument navigation. | Arcturus | Wikipedia | 380 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
Arcturus had several other names that described its significance to indigenous Polynesians. In the Society Islands, Arcturus, called Ana-tahua-taata-metua-te-tupu-mavae ("a pillar to stand by"), was one of the ten "pillars of the sky", bright stars that represented the ten heavens of the Tahitian afterlife. In Hawaii, the pattern of Boötes was called Hoku-iwa, meaning "stars of the frigatebird". This constellation marked the path for Hawaiʻiloa on his return to Hawaii from the South Pacific Ocean. The Hawaiians called Arcturus Hoku-leʻa. It was equated to the Tuamotuan constellation Te Kiva, meaning "frigatebird", which could either represent the figure of Boötes or just Arcturus. However, Arcturus may instead be the Tuamotuan star called Turu. The Hawaiian name for Arcturus as a single star was likely Hoku-leʻa, which means "star of gladness", or "clear star". In the Marquesas Islands, Arcturus was probably called Tau-tou and was the star that ruled the month approximating January. The Māori and Moriori called it Tautoru, a variant of the Marquesan name and a name shared with Orion's Belt.
In Inuit astronomy, Arcturus is called the Old Man (Uttuqalualuk in Inuit languages) and The First Ones (Sivulliik in Inuit languages).
The Miꞌkmaq of eastern Canada saw Arcturus as Kookoogwéss, the owl.
Early-20th-century Armenian scientist Nazaret Daghavarian theorized that the star commonly referred to in Armenian folklore as Gutani astgh (Armenian: Գութանի աստղ; lit. star of the plow) was in fact Arcturus, as the constellation of Boötes was called "Ezogh" (Armenian: Եզող; lit. the person who is plowing) by Armenians.
In popular culture
In Ancient Rome, the star's celestial activity was supposed to portend tempestuous weather, and a personification of the star acts as narrator of the prologue to Plautus' comedy Rudens (circa 211 BC). | Arcturus | Wikipedia | 484 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
The Kāraṇḍavyūha Sūtra, compiled at the end of the 4th century or beginning of the 5th century, names one of Avalokiteśvaras meditative absorptions as "The face of Arcturus".
One of the possible etymologies offered for the name "Arthur" assumes that it is derived from "Arcturus" and that the late 5th to early 6th-century figure on whom the myth of King Arthur is based was originally named for the star.
In the Middle Ages, Arcturus was considered a Behenian fixed star and attributed to the stone jasper and the plantain herb. Cornelius Agrippa listed its kabbalistic sign under the alternate name Alchameth.
Arcturus's light was employed in the mechanism used to open the 1933 Chicago World's Fair. The star was chosen as it was thought that light from Arcturus had started its journey at about the time of the previous Chicago World's Fair in 1893 (at 36.7 light-years away, the light actually started in 1896).
At the height of the American Civil War, President Abraham Lincoln observed Arcturus through a 9.6-inch refractor telescope when he visited the Naval Observatory in Washington, D.C., in August 1863. | Arcturus | Wikipedia | 261 | 3072 | https://en.wikipedia.org/wiki/Arcturus | Physical sciences | Notable stars | null |
Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and τ Scorpii near the center of the constellation. Distinctly reddish when viewed with the naked eye, Antares is a slow irregular variable star that ranges in brightness from an apparent visual magnitude of +0.6 down to +1.6. It is on average the fifteenth-brightest star in the night sky. Antares is the brightest and most evolved stellar member of the Scorpius–Centaurus association, the nearest OB association to the Sun. It is located about from Earth at the rim of the Upper Scorpius subgroup, and is illuminating the Rho Ophiuchi cloud complex in its foreground.
Classified as spectral type M1.5Iab-Ib, Antares is a red supergiant, a large evolved massive star and one of the largest stars visible to the naked eye. If placed at the center of the Solar System, it would extend out to somewhere in the asteroid belt. Its mass is calculated to be around 13 or 15 to 16 times that of the Sun. Antares appears as a single star when viewed with the naked eye, but it is actually a binary star system, with its two components called α Scorpii A and α Scorpii B. The brighter of the pair is the red supergiant, while the fainter is a hot main sequence star of magnitude 5.5. They have a projected separation of about .
Its traditional name Antares derives from the Ancient Greek , meaning "rival to Ares", due to the similarity of its reddish hue to the appearance of the planet Mars.
Nomenclature | Antares | Wikipedia | 377 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
α Scorpii (Latinised to Alpha Scorpii) is the star's Bayer designation. Antares has the Flamsteed designation 21 Scorpii, as well as catalogue designations such as HR 6134 in the Bright Star Catalogue and HD 148478 in the Henry Draper Catalogue. As a prominent infrared source, it appears in the Two Micron All-Sky Survey catalogue as 2MASS J16292443-2625549 and the Infrared Astronomical Satellite (IRAS) Sky Survey Atlas catalogue as IRAS 16262–2619. It is also catalogued as a double star WDS J16294-2626 and CCDM J16294-2626. Antares is a variable star and is listed in the General Catalogue of Variable Stars, but as a Bayer-designated star it does not have a separate variable star designation.
Its traditional name Antares derives from the Ancient Greek , meaning "rival to Ares", due to the similarity of its reddish hue to the appearance of the planet Mars. The comparison of Antares with Mars may have originated with early Mesopotamian astronomers which is considered an outdated speculation, because the name of this star in Mesopotamian astronomy has always been "heart of Scorpion" and it was associated with the goddess Lisin. Some scholars have speculated that the star may have been named after Antar, or Antarah ibn Shaddad, the Arab warrior-hero celebrated in the pre-Islamic poems Mu'allaqat. However, the name "Antares" is already proven in the Greek culture, e.g. in Ptolemy's Almagest and Tetrabiblos. In 2016, the International Astronomical Union organised a Working Group on Star Names (WGSN) to catalog and standardise proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Antares for the star α Scorpii A. It is now so entered in the IAU Catalog of Star Names.
Observation
Antares is visible all night around May 31 of each year, when the star is at opposition to the Sun. Antares then rises at dusk and sets at dawn as seen at the equator. | Antares | Wikipedia | 465 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
For two to three weeks on either side of November 30, Antares is not visible in the night sky from mid-northern latitudes, because it is near conjunction with the Sun. In higher northern latitudes, Antares is only visible low in the south in summertime. Higher than 64° northern latitude, the star does not rise at all.
Antares is easier to see from the southern hemisphere due to its southerly declination. In the whole of Antarctica, the star is circumpolar as the whole continent is above 64° S latitude.
History
Radial velocity variations were observed in the spectrum of Antares in the early 20th century, and attempts were made to derive spectroscopic orbits. It became apparent that the small variations could not be due to orbital motion, and they were actually caused by pulsation of the star's atmosphere. Even in 1928, it was calculated that the size of the star must vary by about 20%.
Antares was first reported to have a companion star by Johann Tobias Bürg during an occultation on April 13, 1819, although this was not widely accepted and dismissed as a possible atmospheric effect. It was then observed by Scottish astronomer James William Grant FRSE while in India on 23 July 1844. It was rediscovered by Ormsby M. Mitchel in 1846 and measured by William Rutter Dawes in April 1847.
In 1952, Antares was reported to vary in brightness. A photographic magnitude range from 3.00 to 3.16 was described. The brightness has been monitored by the American Association of Variable Star Observers since 1945, and it has been classified as an LC slow irregular variable star, whose apparent magnitude slowly varies between extremes of +0.6 and +1.6, although usually near magnitude +1.0. There is no obvious periodicity, but statistical analyses have suggested periods of 1,733 days or days. No separate long secondary period has been detected, although it has been suggested that primary periods longer than a thousand days are analogous to long secondary periods.
Research published in 2018 demonstrated that Ngarrindjeri Aboriginal people from South Australia observed the variability of Antares and incorporated it into their oral traditions as Waiyungari (meaning 'red man').
Occultations and conjunctions | Antares | Wikipedia | 460 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
Antares is 4.57 degrees south of the ecliptic, one of four first magnitude stars within 6° of the ecliptic (the others are Spica, Regulus and Aldebaran), so it can be occulted by the Moon. The occultation of 31 July 2009 was visible in much of southern Asia and the Middle East. Every year around December 2 the Sun passes 5° north of Antares. Lunar occultations of Antares are fairly common, depending on the 18.6-year cycle of the lunar nodes. The last cycle ended in 2010 and the next begins in 2023. Shown at right is a video of a reappearance event, clearly showing events for both components.
Antares can also be occulted by the planets, e.g. Venus, but these events are rare. The last occultation of Antares by Venus took place on September 17, 525 BC; the next one will be November 17, 2400. Other planets have been calculated not to have occulted Antares over the last millennium, nor will they in the next millennium, as most planets stay near the ecliptic and pass north of Antares. Venus will be extremely near Antares on October 19, 2117, and every eight years thereafter through to October 29, 2157, it will pass south of the star.
Illumination of Rho Ophiuchi cloud complex
Antares is the brightest and most evolved stellar member of the Scorpius–Centaurus association, the nearest OB association to the Sun. It is a member of the Upper Scorpius subgroup of the association, which contains thousands of stars with a mean age of 11 million years. Antares is located about from Earth at the rim of the Upper Scorpius subgroup, and is illuminating the Rho Ophiuchi cloud complex in its foreground. The illuminated cloud is sometimes referred to as the Antares Nebula or is otherwise identified as VdB 107.
Stellar system
α Scorpii is a double star that is thought to form a binary system. The best calculated orbit for the stars is still considered to be unreliable. It describes an almost circular orbit seen nearly edge-on, with a period of 1,218 years and a semi-major axis of about . Other recent estimates of the period have ranged from 880 years for a calculated orbit, to 2,562 years for a simple Kepler's Law estimate. | Antares | Wikipedia | 493 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
Early measurements of the pair found them to be about apart in 1847–49, or apart in 1848. More modern observations consistently give separations around . The variations in the separation are often interpreted as evidence of orbital motion, but are more likely to be simply observational inaccuracies with very little true relative motion between the two components.
The pair have a projected separation of about 529 astronomical units (AU) (≈ 80 billion km) at the estimated distance of Antares, giving a minimum value for the distance between them. Spectroscopic examination of the energy states in the outflow of matter from the companion star suggests that the latter is over beyond the primary (about 33 billion km).
Antares
Antares is a red supergiant star with a stellar classification of M1.5Iab-Ib, and is indicated to be a spectral standard for that class. Due to the nature of the star, the derived parallax measurements have large errors, so that the true distance of Antares is approximately from the Sun.
The brightness of Antares at visual wavelengths is about 10,000 times that of the Sun, but because the star radiates a considerable part of its energy in the infrared part of the spectrum, the true bolometric luminosity is around 100,000 times that of the Sun. There is a large margin of error assigned to values for the bolometric luminosity, typically 30% or more. There is also considerable variation between values published by different authors, for example and published in 2012 and 2013.
The mass of the star has been calculated to be about , or . Comparison of the effective temperature and luminosity of Antares to theoretical evolutionary tracks for massive stars suggest a progenitor mass of and an age of 12 million years (MYr), or an initial mass of and an age of 11 to 15 MYr. Comparison of observations from antiquity to theoretical evolutionary tracks suggests an initial mass of , or the possibility that Antares is on a blue loop with an initial mass of (while excluding as a possible mass estimate). These correspond to ages from 11.8 to 17.3 MYr. These initial mass estimates mean that Antares may have once resembled massive blue stars like the members of the Acrux system, which have similar initial masses (both Antares and Acrux are members of the wider Scorpius–Centaurus association). Massive stars like Antares are expected to explode as supernovae. | Antares | Wikipedia | 506 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
Like most cool supergiants, Antares's size has much uncertainty due to the tenuous and translucent nature of the extended outer regions of the star. Defining an effective temperature is difficult due to spectral lines being generated at different depths in the atmosphere, and linear measurements produce different results depending on the wavelength observed. In addition, Antares pulsates in size, varying its radius by 19%. It also varies in temperature by 150 K, lagging 70 days behind radial velocity changes which are likely to be caused by the pulsations.
The diameter of Antares can be measured most accurately using interferometry or observing lunar occultations events. An apparent diameter from occultations 41.3 ± 0.1 milliarcseconds has been published. Interferometry allows synthesis of a view of the stellar disc, which is then represented as a limb-darkened disk surrounded by an extended atmosphere. The diameter of the limb-darkened disk was measured as in 2009 and in 2010. The linear radius of the star can be calculated from its angular diameter and distance. However, the distance to Antares is not known with the same accuracy as modern measurements of its diameter.
An estimate obtained by interferometry in 1925 by Francis G. Pease at the Mount Wilson Observatory gave Antares a diameter of , equal to approximately , making it the then largest star known. Antares is now known to be somewhat larger; for instance, the Hipparcos satellite's trigonometric parallax of with modern angular diameter estimates lead to a radius of about . Older radii estimates exceeding were derived from older measurements of the diameter, but those measurements are likely to have been affected by asymmetry of the atmosphere and the narrow range of infrared wavelengths observed; Antares has an extended shell which radiates strongly at those particular wavelengths. Despite its large size compared to the Sun, Antares is dwarfed by even larger red supergiants, such as VY Canis Majoris, KY Cygni, RW Cephei or Mu Cephei.
Antares, like the similarly sized red supergiant Betelgeuse in the constellation Orion, will almost certainly explode as a supernova, probably in million years. For a few months, the Antares supernova could be as bright as the full moon and be visible in daytime. | Antares | Wikipedia | 478 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
Antares B
Antares B is a magnitude 5.5 blue-white main-sequence star of spectral type B2.5V; it also has numerous unusual spectral lines suggesting it has been polluted by matter ejected by Antares. It is assumed to be a relatively normal early-B main sequence star with a mass around , a temperature around , and a radius of about . As it falls short of the mass limit required for stars to undergo a supernova, it will likely expand into a red giant before dying as a massive white dwarf similar to Sirius B.
Antares B is normally difficult to see in small telescopes due to glare from Antares, but can sometimes be seen in apertures over . It is often described as green, but this is probably either a contrast effect, or the result of the mixing of light from the two stars when they are seen together through a telescope and are too close to be completely resolved. Antares B can sometimes be observed with a small telescope for a few seconds during lunar occultations while Antares is hidden by the Moon. Antares B appears a profound blue or bluish-green color, in contrast to the orange-red Antares.
Etymology and mythology
In the Babylonian star catalogues dating from at least 1100 BCE, Antares was called GABA GIR.TAB, "the Breast of the Scorpion". In MUL.APIN, which dates between 1100 and 700 BC, it is one of the stars of Ea in the southern sky and denotes the breast of the Scorpion goddess Ishhara. Later names that translate as "the Heart of Scorpion" include from the Arabic . This had been directly translated from the Ancient Greek . was a calque of the Greek name rendered in Latin.
In ancient Mesopotamia, Antares may have been known by various names: Urbat, Bilu-sha-ziri ("the Lord of the Seed"), Kak-shisa ("the Creator of Prosperity"), Dar Lugal ("The King"), Masu Sar ("the Hero and the King"), and Kakkab Bir ("the Vermilion Star"). In ancient Egypt, Antares represented the scorpion goddess Serket (and was the symbol of Isis in the pyramidal ceremonies). It was called "the red one of the prow". | Antares | Wikipedia | 478 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
In Persia, Antares was known as one of the four "royal stars". In India, it with σ Scorpii and τ Scorpii were Jyeshthā (the eldest or biggest, probably attributing its huge size), one of the nakshatra (Hindu lunar mansions).
The ancient Chinese called Antares 心宿二 (Xīnxiù'èr, "second star of the Heart"), because it was the second star of the mansion Xin (心). It was the national star of the Shang dynasty, and it was sometimes referred to as () because of its reddish appearance.
The Māori people of New Zealand call Antares Rēhua, and regard it as the chief of all the stars especially the Matariki. Rēhua is father of Puanga/Puaka (Rigel), an important star in the calculation of the Māori calendar. The Wotjobaluk Koori people of Victoria, Australia, knew Antares as Djuit, son of Marpean-kurrk (Arcturus); the stars on each side represented his wives. The Kulin Kooris saw Antares (Balayang) as the brother of Bunjil (Altair).
In culture
Antares appears in the flag of Brazil, which displays 27 stars, each representing a federated unit of Brazil. Antares represents the state of Piauí.
The 1995 Oldsmobile Antares concept car is named after the star.
Antares is one of the medieval Behenian fixed stars. | Antares | Wikipedia | 315 | 3076 | https://en.wikipedia.org/wiki/Antares | Physical sciences | Notable stars | Astronomy |
Aldebaran () (Proto-Semitic *dVbr- “bee”) is a star located in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Aldebaran varies in brightness from an apparent visual magnitude 0.75 down to 0.95, making it the brightest star in the constellation, as well as (typically) the fourteenth-brightest star in the night sky. It is positioned at a distance of approximately 65 light-years from the Sun. The star lies along the line of sight to the nearby Hyades cluster.
Aldebaran is a red giant, meaning that it is cooler than the Sun with a surface temperature of , but its radius is about 45 times the Sun's, so it is over 400 times as luminous. As a giant star, it has moved off the main sequence on the Hertzsprung–Russell diagram after depleting its supply of hydrogen in the core. The star spins slowly and takes 520 days to complete a rotation. Aldebaran is believed to host a planet several times the mass of Jupiter, named .
Nomenclature
The traditional name Aldebaran derives from the Arabic (), meaning , because it seems to follow the Pleiades. In 2016, the International Astronomical Union Working Group on Star Names (WGSN) approved the proper name Aldebaran for this star.
Aldebaran is the brightest star in the constellation Taurus, with the Bayer designation α Tauri, latinised as Alpha Tauri. It has the Flamsteed designation 87 Tauri as the 87th star in the constellation of approximately 7th magnitude or brighter, ordered by right ascension. It also has the Bright Star Catalogue number 1457, the HD number 29139, and the Hipparcos catalogue number 21421, mostly seen in scientific publications.
It is a variable star listed in the General Catalogue of Variable Stars, but it is listed using its Bayer designation and does not have a separate variable star designation. | Aldebaran | Wikipedia | 425 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
Aldebaran and several nearby stars are included in double star catalogues such as the Washington Double Star Catalog as WDS 04359+1631 and the Aitken Double Star Catalogue as ADS 3321. It was included with an 11th-magnitude companion as a double star as H IV 66 in the Herschel Catalogue of Double Stars and Σ II 2 in the Struve Double Star Catalog, and together with a 14th-magnitude star as β 550 in the Burnham Double Star Catalogue.
Observation
Aldebaran is one of the easiest stars to find in the night sky, partly due to its brightness and partly due to being near one of the more noticeable asterisms in the sky. Following the three stars of Orion's belt in the direction opposite to Sirius, the first bright star encountered is Aldebaran.
It is best seen at midnight between late November and early December.
The star is, by chance, in the line of sight between the Earth and the Hyades, so it has the appearance of being the brightest member of the open cluster, but the cluster that forms the bull's-head-shaped asterism is more than twice as far away, at about 150 light years.
Aldebaran is 5.47 degrees south of the ecliptic and so can be occulted by the Moon. Such occultations occur when the Moon's ascending node is near the autumnal equinox. A series of 49 occultations occurred starting on 29 January 2015 and ending at 3 September 2018. Each event was visible from points in the northern hemisphere or close to the equator; people in e.g. Australia or South Africa can never observe an Aldebaran occultation since it is too far south of the ecliptic. A reasonably accurate estimate for the diameter of Aldebaran was obtained during the occultation of 22 September 1978. In the 2020s, Aldebaran is in conjunction in ecliptic longitude with the sun around May 30 of each year.
With a near-infrared J band magnitude of −2.1, only Betelgeuse (−2.9), R Doradus (−2.6), and Arcturus (−2.2) are brighter at that wavelength.
Observational history | Aldebaran | Wikipedia | 464 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
On 11 March AD 509, a lunar occultation of Aldebaran was observed in Athens, Greece. English astronomer Edmund Halley studied the timing of this event, and in 1718 concluded that Aldebaran must have changed position since that time, moving several minutes of arc further to the north. This, as well as observations of the changing positions of stars Sirius and Arcturus, led to the discovery of proper motion. Based on present day observations, the position of Aldebaran has shifted 7′ in the last 2000 years; roughly a quarter the diameter of the full moon. Due to precession of the equinoxes, 5,000 years ago the vernal equinox was close to Aldebaran. Between 420,000 and 210,000 years ago, Aldebaran was the brightest star in the night sky, peaking in brightness 320,000 years ago with an apparent magnitude of .
English astronomer William Herschel discovered a faint companion to Aldebaran in 1782; an 11th-magnitude star at an angular separation of 117″. This star was shown to be itself a close double star by S. W. Burnham in 1888, and he discovered an additional 14th-magnitude companion at an angular separation of 31″. Follow-on measurements of proper motion showed that Herschel's companion was diverging from Aldebaran, and hence they were not physically connected. However, the companion discovered by Burnham had almost exactly the same proper motion as Aldebaran, suggesting that the two formed a wide binary star system.
Working at his private observatory in Tulse Hill, England, in 1864 William Huggins performed the first studies of the spectrum of Aldebaran, where he was able to identify the lines of nine elements, including iron, sodium, calcium, and magnesium. In 1886, Edward C. Pickering at the Harvard College Observatory used a photographic plate to capture fifty absorption lines in the spectrum of Aldebaran. This became part of the Draper Catalogue, published in 1890. By 1887, the photographic technique had improved to the point that it was possible to measure a star's radial velocity from the amount of Doppler shift in the spectrum. By this means, the recession velocity of Aldebaran was estimated as (48 km/s), using measurements performed at Potsdam Observatory by Hermann C. Vogel and his assistant Julius Scheiner. | Aldebaran | Wikipedia | 491 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
Aldebaran was observed using an interferometer attached to the Hooker Telescope at the Mount Wilson Observatory in 1921 in order to measure its angular diameter, but it was not resolved in these observations.
The extensive history of observations of Aldebaran led to it being included in the list of 33 stars chosen as benchmarks for the Gaia mission to calibrate derived stellar parameters. It had previously been used to calibrate instruments on board the Hubble Space Telescope.
Physical characteristics
Aldebaran is listed as the spectral standard for type K5+ III stars. Its spectrum shows that it is a giant star that has evolved off the main sequence band of the HR diagram after exhausting the hydrogen at its core. The collapse of the center of the star into a degenerate helium core has ignited a shell of hydrogen outside the core and Aldebaran is now on the red giant branch (RGB).
The effective temperature of Aldebaran's photosphere is . It has a surface gravity of , typical for a giant star, but around 25 times lower than the Earth's and 700 times lower than the Sun's. Its metallicity is about 30% lower than the Sun's.
Measurements by the Hipparcos satellite and other sources put Aldebaran around away. Asteroseismology has determined that it is about 16% more massive than the Sun, yet it shines with 518 times the Sun's luminosity due to the expanded radius. The angular diameter of Aldebaran has been measured many times. The value adopted as part of the Gaia benchmark calibration is . It is 44 times the diameter of the Sun, approximately 61 million kilometres.
Aldebaran is a slightly variable star, assigned to the slow irregular type LB. The General Catalogue of Variable Stars indicates variation between apparent magnitude 0.75 and 0.95 from historical reports. Modern studies show a smaller amplitude, with some showing almost no variation. Hipparcos photometry shows an amplitude of only about 0.02 magnitudes and a possible period around 18 days. Intensive ground-based photometry showed variations of up to 0.03 magnitudes and a possible period around 91 days. Analysis of observations over a much longer period still find a total amplitude likely to be less than 0.1 magnitudes, and the variation is considered to be irregular. | Aldebaran | Wikipedia | 487 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
The photosphere shows abundances of carbon, oxygen, and nitrogen that suggest the giant has gone through its first dredge-up stage—a normal step in the evolution of a star into a red giant during which material from deep within the star is brought up to the surface by convection. With its slow rotation, Aldebaran lacks a dynamo needed to generate a corona and hence is not a source of hard X-ray emission. However, small scale magnetic fields may still be present in the lower atmosphere, resulting from convection turbulence near the surface. The measured strength of the magnetic field on Aldebaran is . Any resulting soft X-ray emissions from this region may be attenuated by the chromosphere, although ultraviolet emission has been detected in the spectrum. The star is currently losing mass at a rate of (about one Earth mass in 300,000 years) with a velocity of . This stellar wind may be generated by the weak magnetic fields in the lower atmosphere.
Beyond the chromosphere of Aldebaran is an extended molecular outer atmosphere (MOLsphere) where the temperature is cool enough for molecules of gas to form. This region lies at about 2.5 times the radius of the star and has a temperature of about . The spectrum reveals lines of carbon monoxide, water, and titanium oxide. Outside the MOLSphere, the stellar wind continues to expand until it reaches the termination shock boundary with the hot, ionized interstellar medium that dominates the Local Bubble, forming a roughly spherical astrosphere with a radius of around , centered on Aldebaran.
Visual companions
Five faint stars appear close to Aldebaran in the sky. These double star components were given upper-case Latin letter designations more or less in the order of their discovery, with the letter A reserved for the primary star. Some characteristics of these components, including their position relative to Aldebaran, are shown in the table. | Aldebaran | Wikipedia | 395 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
Some surveys, for example Gaia Data Release 2, have indicated that Alpha Tauri B may have about the same proper motion and parallax as Aldebaran and thus may be a physical binary system. These measurements are difficult, since the dim B component appears so close to the bright primary star, and the margin of error is too large to establish (or exclude) a physical relationship between the two. So far neither the B component, nor anything else, has been unambiguously shown to be physically associated with Aldebaran. The Gaia Data Release 3 again suggest a close distance to Aldebaran and similar proper motions. With a parallax of 47.25 milliarcseconds, this translates into a distance of . The NASA Exoplanet Archive recognizes Aldebaran as a binary star, with Aldebaran B being the secondary star. A spectral type of M2.5 has been published for Alpha Tauri B.
Alpha Tauri CD is a binary system with the C and D component stars gravitationally bound to and co-orbiting each other. These co-orbiting stars have been shown to be located far beyond Aldebaran and are members of the Hyades star cluster. As with the rest of the stars in the cluster they do not physically interact with Aldebaran in any way.
Planetary system
In 1993 radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Aldebaran exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. The measurements for Aldebaran implied a companion with a minimum mass 11.4 times that of Jupiter in a 643-day orbit at a separation of in a mildly eccentric orbit. However, all three stars surveyed showed similar oscillations yielding similar companion masses, and the authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion. | Aldebaran | Wikipedia | 404 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
In 2015 a study showed stable long-term evidence for both a planetary companion and stellar activity. An asteroseismic analysis of the residuals to the planet fit has determined that Aldebaran b has a minimum mass of Jupiter masses, and that when the star was on the main sequence it would have given this planet Earth-like levels of illumination and therefore, potentially, temperature. This would place it and any of its moons in the habitable zone. Follow-up study in 2019 have found the evidence for planetary existence inconclusive though.
Etymology and mythology
Aldebaran was originally ( in Arabic), meaning , since it follows the Pleiades; in fact, the Arabs sometimes also applied the name to the Hyades as a whole. A variety of transliterated spellings have been used, with the current Aldebaran becoming standard relatively recently.
Mythology
This easily seen and striking star in its suggestive asterism is a popular subject for ancient and modern myths.
Mexican culture: For the Seris of northwestern Mexico, this star provides light for the seven women giving birth (Pleiades). It has three names: , , and (). The lunar month corresponding to October is called .
Australian Aboriginal culture: amongst indigenous people of the Clarence River, in north-eastern New South Wales, this star is the ancestor Karambal, who stole another man's wife. The woman's husband tracked him down and burned the tree in which he was hiding. It is believed that he rose to the sky as smoke and became the star Aldebaran.
Persian culture: Aldebaran is considered one of the 4 "royal stars".
Names in other languages
In Indian astronomy it is identified as the lunar station Rohini. In Hindu mythology, Rohini is one of the twenty-seven daughters of the sage-king Daksha and Asikni, and the favourite wife of the moon god, Chandra.
In Ancient Greek it has been called , literally or . | Aldebaran | Wikipedia | 407 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
In Chinese, (), meaning , refers to an asterism consisting of Aldebaran, ε Tauri, δ3 Tauri, δ1 Tauri, γ Tauri, 71 Tauri and λ Tauri. Consequently, the Chinese name for Aldebaran itself is (), .
In Hawaiian, the star is named Kapuahi.
In Biblical Hebrew, עָשׁ (ʿāš) in Job 9:9 and עַ֫יִשׁ (ʿayiš) in Job 38:32 have been identified with it and translated accordingly in English versions such as NJPS and REB.
In modern culture
As the brightest star in a Zodiac constellation, it is given great significance within astrology.
Irish singer and composer Enya has a piece released on her eponymous album in 1986, which lyricist Roma Ryan titled Aldebaran after the star in Taurus.
The name Aldebaran or Alpha Tauri has been adopted many times, including
Aldebaran Rock in Antarctica
United States Navy stores ship and
proposed micro-satellite launch vehicle Aldebaran
French company Aldebaran Robotics
Fashion brand AlphaTauri
Formula 1 team Scuderia AlphaTauri, active from to , previously known as Toro Rosso
One of the chariot race horses owned by Sheikh Ilderim in the movie Ben-Hur
The star also appears in works of fiction such as Far from the Madding Crowd (1874) and Down and Out in Paris and London (1933). It is frequently seen in science fiction, including the Lensman series (1948–1954), Fallen Dragon (2001) and passingly in Kim Stanley Robinson's "Blue Mars" (1996). Aldebaran is associated with Hastur, also known as The King in Yellow, in the horror stories of Robert W. Chambers.
Aldebaran regularly features in conspiracy theories as one of the origins of extraterrestrial aliens, often linked to Nazi UFOs. A well-known example is the German conspiracy theorist Axel Stoll, who considered the star the home of the Aryan race and the target of expeditions by the Wehrmacht.
The planetary exploration probe Pioneer 10 is no longer powered or in contact with Earth, but its trajectory is taking it in the general direction of Aldebaran. It is expected to make its closest approach in about two million years. | Aldebaran | Wikipedia | 475 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
The Austrian chemist Carl Auer von Welsbach proposed the name aldebaranium (chemical symbol Ad) for a rare earth element that he (among others) had found. Today, it is called ytterbium (symbol Yb). | Aldebaran | Wikipedia | 51 | 3077 | https://en.wikipedia.org/wiki/Aldebaran | Physical sciences | Notable stars | Astronomy |
Altair is the brightest star in the constellation of Aquila and the twelfth-brightest star in the night sky. It has the Bayer designation Alpha Aquilae, which is Latinised from α Aquilae and abbreviated Alpha Aql or α Aql. Altair is an A-type main-sequence star with an apparent visual magnitude of 0.77 and is one of the vertices of the Summer Triangle asterism; the other two vertices are marked by Deneb and Vega. It is located at a distance of from the Sun. Altair is currently in the G-cloud—a nearby interstellar cloud, an accumulation of gas and dust.
Altair rotates rapidly, with a velocity at the equator of approximately 286 km/s. This is a significant fraction of the star's estimated breakup speed of 400 km/s. A study with the Palomar Testbed Interferometer revealed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation. Other interferometric studies with multiple telescopes, operating in the infrared, have imaged and confirmed this phenomenon.
Nomenclature
α Aquilae (Latinised to Alpha Aquilae) is the star's Bayer designation. The traditional name Altair has been used since medieval times. It is an abbreviation of the Arabic phrase Al-Nisr Al-Ṭa'ir, "".
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Altair for this star. It is now so entered in the IAU Catalog of Star Names.
Physical characteristics
Along with β Aquilae and γ Aquilae, Altair forms the well-known line of stars sometimes referred to as the Family of Aquila or Shaft of Aquila. | Altair | Wikipedia | 404 | 3078 | https://en.wikipedia.org/wiki/Altair | Physical sciences | Notable stars | Astronomy |
Altair is a type-A main-sequence star with about 1.8 times the mass of the Sun and 11 times its luminosity. It is thought to be a young star close to the zero age main sequence at about 100 million years old, although previous estimates gave an age closer to one billion years old. Altair rotates rapidly, with a rotational period of under eight hours; for comparison, the equator of the Sun makes a complete rotation in a little more than 25 days, but Altair's rotation is similar to, and slightly faster than, those of Jupiter and Saturn. Like those two planets, its rapid rotation causes the star to be oblate; its equatorial diameter is over 20 percent greater than its polar diameter.
Satellite measurements made in 1999 with the Wide Field Infrared Explorer showed that the brightness of Altair fluctuates slightly, varying by just a few thousandths of a magnitude with several different periods less than 2 hours. As a result, it was identified in 2005 as a Delta Scuti variable star. Its light curve can be approximated by adding together a number of sine waves, with periods that range between 0.8 and 1.5 hours. It is a weak source of coronal X-ray emission, with the most active sources of emission being located near the star's equator. This activity may be due to convection cells forming at the cooler equator.
Rotational effects
The angular diameter of Altair was measured interferometrically by R. Hanbury Brown and his co-workers at Narrabri Observatory in the 1960s. They found a diameter of 3milliarcseconds. Although Hanbury Brown et al. realized that Altair would be rotationally flattened, they had insufficient data to experimentally observe its oblateness. Later, using infrared interferometric measurements made by the Palomar Testbed Interferometer in 1999 and 2000, Altair was found to be flattened. This work was published by G. T. van Belle, David R. Ciardi and their co-authors in 2001. | Altair | Wikipedia | 417 | 3078 | https://en.wikipedia.org/wiki/Altair | Physical sciences | Notable stars | Astronomy |
Theory predicts that, owing to Altair's rapid rotation, its surface gravity and effective temperature should be lower at the equator, making the equator less luminous than the poles. This phenomenon, known as gravity darkening or the von Zeipel effect, was confirmed for Altair by measurements made by the Navy Precision Optical Interferometer in 2001, and analyzed by Ohishi et al. (2004) and Peterson et al. (2006). Also, A. Domiciano de Souza et al. (2005) verified gravity darkening using the measurements made by the Palomar and Navy interferometers, together with new measurements made by the VINCI instrument at the VLTI.
Altair is one of the few stars for which a direct image has been obtained. In 2006 and 2007, J. D. Monnier and his coworkers produced an image of Altair's surface from 2006 infrared observations made with the MIRC instrument on the CHARA array interferometer; this was the first time the surface of any main-sequence star, apart from the Sun, had been imaged. The false-color image was published in 2007. The equatorial radius of the star was estimated to be 2.03 solar radii, and the polar radius 1.63 solar radii—a 25% increase of the stellar radius from pole to equator. The polar axis is inclined by about 60° to the line of sight from the Earth.
Etymology, mythology and culture
The term Al Nesr Al Tair appeared in Al Achsasi al Mouakket's catalogue, which was translated into Latin as Vultur Volans. This name was applied by the Arabs to the asterism of Altair, β Aquilae and γ Aquilae and probably goes back to the ancient Babylonians and Sumerians, who called Altair "the eagle star". The spelling Atair has also been used. Medieval astrolabes of England and Western Europe depicted Altair and Vega as birds.
The Koori people of Victoria also knew Altair as Bunjil, the wedge-tailed eagle, and β and γ Aquilae are his two wives the black swans. The people of the Murray River knew the star as Totyerguil. The Murray River was formed when Totyerguil the hunter speared Otjout, a giant Murray cod, who, when wounded, churned a channel across southern Australia before entering the sky as the constellation Delphinus. | Altair | Wikipedia | 509 | 3078 | https://en.wikipedia.org/wiki/Altair | Physical sciences | Notable stars | Astronomy |
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