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20,400 | In 1994, world production of was around 1.9 million tonnes and grew to 2.2 million in 2006, most of which was at a concentration of 70% or less. In that year, bulk 30% sold for around 0.54 USD/kg, equivalent to US$1.50/kg (US$0.68/lb) on a "100% basis". | https://en.wikipedia.org/wiki?curid=14403 |
20,401 | Hydrogen peroxide occurs in surface water, groundwater and in the atmosphere. It forms upon illumination or natural catalytic action by substances contained in water. Sea water contains 0.5 to 14 μg/L of hydrogen peroxide, freshwater 1 to 30 μg/L and air 0.1 to 1 parts per billion. | https://en.wikipedia.org/wiki?curid=14403 |
20,402 | Hydrogen peroxide decomposes to form water and oxygen with a Δ"H" of –2884.5 kJ/kg and a ΔS of 70.5 J/(mol·K): | https://en.wikipedia.org/wiki?curid=14403 |
20,403 | The rate of decomposition increases with rise in temperature, concentration, and pH ( being unstable under alkaline conditions), with cool, dilute, and acidic solutions showing the best stability. Decomposition is catalysed by various redox-active ions or compounds, including most transition metals and their compounds ... | https://en.wikipedia.org/wiki?curid=14403 |
20,404 | The redox properties of hydrogen peroxide depend on pH as acidic conditions exacerbate the power of oxidizing agents and basic conditions exacerbate the power of reducing agents. As hydrogen peroxide exhibits ambivalent redox properties, being simultaneously an oxidizer or a reductant, its redox behavior immediately de... | https://en.wikipedia.org/wiki?curid=14403 |
20,405 | In acidic solutions, is a powerful oxidizer, stronger than chlorine, chlorine dioxide, and potassium permanganate. When used for cleaning laboratory glassware, a solution of hydrogen peroxide and sulfuric acid is referred to as Piranha solution. | https://en.wikipedia.org/wiki?curid=14403 |
20,406 | Under alkaline conditions, however, some of these reactions reverse; for example, is oxidized to (as ). | https://en.wikipedia.org/wiki?curid=14403 |
20,407 | In basic solutions, hydrogen peroxide is a strong reductant and can reduce a variety of inorganic ions. When acts as a reducing agent, oxygen gas is also produced. For example, hydrogen peroxide will reduce sodium hypochlorite and potassium permanganate, which is a convenient method for preparing oxygen in the laborato... | https://en.wikipedia.org/wiki?curid=14403 |
20,408 | Hydrogen peroxide is frequently used as an oxidizing agent. Illustrative is oxidation of thioethers to sulfoxides: | https://en.wikipedia.org/wiki?curid=14403 |
20,409 | Alkaline hydrogen peroxide is used for epoxidation of electron-deficient alkenes such as acrylic acid derivatives, and for the oxidation of alkylboranes to alcohols, the second step of hydroboration-oxidation. It is also the principal reagent in the Dakin oxidation process. | https://en.wikipedia.org/wiki?curid=14403 |
20,410 | It also converts metal oxides into the corresponding peroxides. For example, upon treatment with hydrogen peroxide, chromic acid ( and ) forms a blue peroxide . | https://en.wikipedia.org/wiki?curid=14403 |
20,411 | This kind of reaction is used industrially to produce peroxoanions. For example, reaction with borax leads to sodium perborate, a bleach used in laundry detergents: | https://en.wikipedia.org/wiki?curid=14403 |
20,412 | Hydrogen peroxide is both an oxidizing agent and reducing agent. The oxidation of hydrogen peroxide by sodium hypochlorite yields singlet oxygen. The net reaction of a ferric ion with hydrogen peroxide is a ferrous ion and oxygen. This proceeds via single electron oxidation and hydroxyl radicals. This is used in some o... | https://en.wikipedia.org/wiki?curid=14403 |
20,413 | Hydrogen peroxide is formed in humans and other animals as a short-lived product in biochemical processes and is toxic to cells. The toxicity is due to oxidation of proteins, membrane lipids and DNA by the peroxide ions. The class of biological enzymes called superoxide dismutase (SOD) is developed in nearly all living... | https://en.wikipedia.org/wiki?curid=14403 |
20,414 | Peroxisomes are organelles found in virtually all eukaryotic cells. They are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, -amino acids, polyamines, and biosynthesis of plasmalogens, ether phospholipids critical for the normal function of mammalian brains and lungs. Upon oxidati... | https://en.wikipedia.org/wiki?curid=14403 |
20,415 | Catalase, another peroxisomal enzyme, uses this to oxidize other substrates, including phenols, formic acid, formaldehyde, and alcohol, by means of a peroxidation reaction: | https://en.wikipedia.org/wiki?curid=14403 |
20,416 | This reaction is important in liver and kidney cells, where the peroxisomes neutralize various toxic substances that enter the blood. Some of the ethanol humans drink is oxidized to acetaldehyde in this way. In addition, when excess accumulates in the cell, catalase converts it to through this reaction: | https://en.wikipedia.org/wiki?curid=14403 |
20,417 | Another origin of hydrogen peroxide is the degradation of adenosine monophosphate which yields hypoxanthine. Hypoxanthine is then oxidatively catabolized first to xanthine and then to uric acid, and the reaction is catalyzed by the enzyme xanthine oxidase: | https://en.wikipedia.org/wiki?curid=14403 |
20,418 | The degradation of guanosine monophosphate yields xanthine as an intermediate product which is then converted in the same way to uric acid with the formation of hydrogen peroxide. | https://en.wikipedia.org/wiki?curid=14403 |
20,419 | Eggs of sea urchin, shortly after fertilization by a sperm, produce hydrogen peroxide. It is then quickly dissociated to HO• radicals. The radicals serve as initiator of radical polymerization, which surrounds the eggs with a protective layer of polymer. | https://en.wikipedia.org/wiki?curid=14403 |
20,420 | The bombardier beetle has a device which allows it to shoot corrosive and foul-smelling bubbles at its enemies. The beetle produces and stores hydroquinone and hydrogen peroxide, in two separate reservoirs in the rear tip of its abdomen. When threatened, the beetle contracts muscles that force the two reactants through... | https://en.wikipedia.org/wiki?curid=14403 |
20,421 | Hydrogen peroxide has roles as a signalling molecule in the regulation of a wide variety of biological processes. The compound is a major factor implicated in the free-radical theory of aging, based on how readily hydrogen peroxide can decompose into a hydroxyl radical and how superoxide radical byproducts of cellular ... | https://en.wikipedia.org/wiki?curid=14403 |
20,422 | About 60% of the world's production of hydrogen peroxide is used for pulp- and paper-bleaching. The second major industrial application is the manufacture of sodium percarbonate and sodium perborate, which are used as mild bleaches in laundry detergents. Sodium percarbonate, which is an adduct of sodium carbonate and h... | https://en.wikipedia.org/wiki?curid=14403 |
20,423 | It is used in the production of various organic peroxides with dibenzoyl peroxide being a high volume example. Peroxy acids, such as peracetic acid and meta-chloroperoxybenzoic acid also are produced using hydrogen peroxide. Hydrogen peroxide has been used for creating organic peroxide-based explosives, such as acetone... | https://en.wikipedia.org/wiki?curid=14403 |
20,424 | Hydrogen peroxide is used in certain waste-water treatment processes to remove organic impurities. In advanced oxidation processing, the Fenton reaction gives the highly reactive hydroxyl radical (•OH). This degrades organic compounds, including those that are ordinarily robust, such as aromatic or halogenated compound... | https://en.wikipedia.org/wiki?curid=14403 |
20,425 | Hydrogen peroxide may be used for the sterilization of various surfaces, including surgical tools, and may be deployed as a vapour (VHP) for room sterilization. demonstrates broad-spectrum efficacy against viruses, bacteria, yeasts, and bacterial spores. In general, greater activity is seen against Gram-positive than G... | https://en.wikipedia.org/wiki?curid=14403 |
20,426 | Hydrogen peroxide is seen as an environmentally safe alternative to chlorine-based bleaches, as it degrades to form oxygen and water and it is generally recognized as safe as an antimicrobial agent by the U.S. Food and Drug Administration (FDA). | https://en.wikipedia.org/wiki?curid=14403 |
20,427 | High-concentration is referred to as "high-test peroxide" (HTP). It can be used either as a monopropellant (not mixed with fuel) or as the oxidizer component of a bipropellant rocket. Use as a monopropellant takes advantage of the decomposition of 70–98% concentration hydrogen peroxide into steam and oxygen. The propel... | https://en.wikipedia.org/wiki?curid=14403 |
20,428 | As a bipropellant, is decomposed to burn a fuel as an oxidizer. Specific impulses as high as 350 s (3.5 kN·s/kg) can be achieved, depending on the fuel. Peroxide used as an oxidizer gives a somewhat lower "I" than liquid oxygen, but is dense, storable, non-cryogenic and can be more easily used to drive gas turbines to ... | https://en.wikipedia.org/wiki?curid=14403 |
20,429 | In the 1940s and 1950s, the Hellmuth Walter KG–conceived turbine used hydrogen peroxide for use in submarines while submerged; it was found to be too noisy and require too much maintenance compared to diesel-electric power systems. Some torpedoes used hydrogen peroxide as oxidizer or propellant. Operator error in the u... | https://en.wikipedia.org/wiki?curid=14403 |
20,430 | Diluted (between 1.9% and 12%) mixed with aqueous ammonia has been used to bleach human hair. The chemical's bleaching property lends its name to the phrase "peroxide blonde". | https://en.wikipedia.org/wiki?curid=14403 |
20,431 | Hydrogen peroxide is also used for tooth whitening. It may be found in most whitening toothpastes. Hydrogen peroxide has shown positive results involving teeth lightness and chroma shade parameters. It works by oxidizing colored pigments onto the enamel where the shade of the tooth may become lighter. Hydrogen peroxide... | https://en.wikipedia.org/wiki?curid=14403 |
20,432 | Hydrogen peroxide reacts with blood as a bleaching agent, and so if a blood stain is fresh, or not too old, liberal application of hydrogen peroxide, if necessary in more than single application, will bleach the stain fully out. After about two minutes of the application, the blood should be firmly blotted out. | https://en.wikipedia.org/wiki?curid=14403 |
20,433 | Hydrogen peroxide reacts with certain di-esters, such as phenyl oxalate ester (cyalume), to produce chemiluminescence; this application is most commonly encountered in the form of glow sticks. | https://en.wikipedia.org/wiki?curid=14403 |
20,434 | Some horticulturalists and users of hydroponics advocate the use of weak hydrogen peroxide solution in watering solutions. Its spontaneous decomposition releases oxygen that enhances a plant's root development and helps to treat root rot (cellular root death due to lack of oxygen) and a variety of other pests. | https://en.wikipedia.org/wiki?curid=14403 |
20,435 | Hydrogen peroxide is used in aquaculture for controlling mortality caused by various microbes. In 2019, the U.S. FDA approved it for control of "Saprolegniasis" in all coldwater finfish and all fingerling and adult coolwater and warmwater finfish, for control of external columnaris disease in warm-water finfish, and fo... | https://en.wikipedia.org/wiki?curid=14403 |
20,436 | Hydrogen peroxide may be used in combination with a UV-light source to remove yellowing from white or light grey acrylonitrile butadiene styrene (ABS) plastics to partially or fully restore the original color. In the retrocomputing scene, this process is commonly referred to as retr0bright. | https://en.wikipedia.org/wiki?curid=14403 |
20,437 | Regulations vary, but low concentrations, such as 5%, are widely available and legal to buy for medical use. Most over-the-counter peroxide solutions are not suitable for ingestion. Higher concentrations may be considered hazardous and typically are accompanied by a safety data sheet (SDS). In high concentrations, hydr... | https://en.wikipedia.org/wiki?curid=14403 |
20,438 | While concentrations up to 35% produce only "white" oxygen bubbles in the skin (and some biting pain) that disappear with the blood within 30-45 minutes concentrations of 98% dissolve paper. However concentrations as low as 3% can be dangerous for the eye because of oxygen evolution within the eye. | https://en.wikipedia.org/wiki?curid=14403 |
20,439 | High-concentration hydrogen peroxide streams, typically above 40%, should be considered hazardous due to concentrated hydrogen peroxide's meeting the definition of a DOT oxidizer according to U.S. regulations, if released into the environment. The EPA Reportable Quantity (RQ) for D001 hazardous wastes is , or approxima... | https://en.wikipedia.org/wiki?curid=14403 |
20,440 | Hydrogen peroxide should be stored in a cool, dry, well-ventilated area and away from any flammable or combustible substances. It should be stored in a container composed of non-reactive materials such as stainless steel or glass (other materials including some plastics and aluminium alloys may also be suitable). Becau... | https://en.wikipedia.org/wiki?curid=14403 |
20,441 | Hydrogen peroxide, either in pure or diluted form, may pose several risks, the main one being that it forms explosive mixtures upon contact with organic compounds. Distillation of hydrogen peroxide at normal pressures is highly dangerous. It is also corrosive, especially when concentrated, but even domestic-strength so... | https://en.wikipedia.org/wiki?curid=14403 |
20,442 | With a significant vapour pressure (1.2 kPa at 50 °C), hydrogen-peroxide vapour is potentially hazardous. According to U.S. NIOSH, the immediately dangerous to life and health (IDLH) limit is only 75 ppm. The U.S. Occupational Safety and Health Administration (OSHA) has established a permissible exposure limit of 1.0 p... | https://en.wikipedia.org/wiki?curid=14403 |
20,443 | Historically, hydrogen peroxide was used for disinfecting wounds, partly because of its low cost and prompt availability compared to other antiseptics. | https://en.wikipedia.org/wiki?curid=14403 |
20,444 | There is conflicting evidence on hydrogen peroxide's effect on wound healing. Some research finds benefit, while other research find delays and healing inhibition. Its use for home treatment of wounds is generally contraindicated. | https://en.wikipedia.org/wiki?curid=14403 |
20,445 | 1.5%-3% Hydrogen peroxide is used as a desinfectant in dentistry, especially in endodotic treatments together with hypochlorite and chlorhexidin and 1-1.5% is also useful for treatment of inflammation of third molars (wisdom teeth). | https://en.wikipedia.org/wiki?curid=14403 |
20,446 | Practitioners of alternative medicine have advocated the use of hydrogen peroxide for various conditions, including emphysema, influenza, AIDS, and in particular cancer. There is no evidence of effectiveness and in some cases it has proved fatal. | https://en.wikipedia.org/wiki?curid=14403 |
20,447 | Both the effectiveness and safety of hydrogen peroxide therapy is scientifically questionable. Hydrogen peroxide is produced by the immune system, but in a carefully controlled manner. Cells called phagocytes engulf pathogens and then use hydrogen peroxide to destroy them. The peroxide is toxic to both the cell and the... | https://en.wikipedia.org/wiki?curid=14403 |
20,448 | Claims that hydrogen peroxide therapy increases cellular levels of oxygen have not been supported. The quantities administered would be expected to provide very little additional oxygen compared to that available from normal respiration. It is also difficult to raise the level of oxygen around cancer cells within a tum... | https://en.wikipedia.org/wiki?curid=14403 |
20,449 | Large oral doses of hydrogen peroxide at a 3% concentration may cause irritation and blistering to the mouth, throat, and abdomen as well as abdominal pain, vomiting, and diarrhea. Ingestion of hydrogen peroxide at concentrations of 35% or higher has been implicated as the cause of numerous gas embolism events resultin... | https://en.wikipedia.org/wiki?curid=14403 |
20,450 | The American Cancer Society states that "there is no scientific evidence that hydrogen peroxide is a safe, effective, or useful cancer treatment." Furthermore, the therapy is not approved by the U.S. FDA. | https://en.wikipedia.org/wiki?curid=14403 |
20,451 | The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The galaxy's name stems from the area of Earth's sky in which it appears, the constell... | https://en.wikipedia.org/wiki?curid=74331 |
20,452 | The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at . The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into qu... | https://en.wikipedia.org/wiki?curid=74331 |
20,453 | combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way. The Andromeda Galaxy has a diameter of about , making it the largest member of the Local Group in terms of extension. | https://en.wikipedia.org/wiki?curid=74331 |
20,454 | The Milky Way and Andromeda galaxies are expected to collide in around 4–5 billion years, merging to potentially form a giant elliptical galaxy or a large lenticular galaxy. | https://en.wikipedia.org/wiki?curid=74331 |
20,455 | With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects, and is visible to the naked eye from Earth on moonless nights, even when viewed from areas with moderate light pollution. | https://en.wikipedia.org/wiki?curid=74331 |
20,456 | Around the year 964, the Persian astronomer Abd al-Rahman al-Sufi was the first to formally describe the Andromeda Galaxy. He referred to it in his "Book of Fixed Stars" as a "nebulous smear" or "small cloud". | https://en.wikipedia.org/wiki?curid=74331 |
20,457 | Star charts of that period labeled it as the "Little Cloud". In 1612, the German astronomer Simon Marius gave an early description of the Andromeda Galaxy based on telescopic observations. Pierre Louis Maupertuis conjectured in 1745 that the blurry spot was an island universe. In 1764, Charles Messier cataloged Androme... | https://en.wikipedia.org/wiki?curid=74331 |
20,458 | In 1864 William Huggins noted that the spectrum of Andromeda differed from that of a gaseous nebula. The spectra of Andromeda displays a continuum of frequencies, superimposed with dark absorption lines that help identify the chemical composition of an object. Andromeda's spectrum is very similar to the spectra of indi... | https://en.wikipedia.org/wiki?curid=74331 |
20,459 | In 1888, Isaac Roberts took one of the first photographs of Andromeda, which was still commonly thought to be a nebula within our galaxy. Roberts mistook Andromeda and similar "spiral nebulae" as star systems being formed. | https://en.wikipedia.org/wiki?curid=74331 |
20,460 | In 1912, Vesto Slipher used spectroscopy to measure the radial velocity of Andromeda with respect to the Solar System—the largest velocity yet measured, at . | https://en.wikipedia.org/wiki?curid=74331 |
20,461 | As early as 1755 the German philosopher Immanuel Kant proposed the hypothesis that the Milky Way is only one of many galaxies, in his book "Universal Natural History and Theory of the Heavens". Arguing that a structure like the Milky Way would look like a circular nebula viewed from above and like an elliptical if view... | https://en.wikipedia.org/wiki?curid=74331 |
20,462 | In 1917, Heber Curtis observed a nova within Andromeda. Searching the photographic record, 11 more novae were discovered. Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred elsewhere in the sky. As a result, he was able to come up with a distance estimate of . He became a p... | https://en.wikipedia.org/wiki?curid=74331 |
20,463 | In 1920, the Great Debate between Harlow Shapley and Curtis took place concerning the nature of the Milky Way, spiral nebulae, and the dimensions of the universe. To support his claim of the Great Andromeda Nebula being, in fact, an external galaxy, Curtis also noted the appearance of dark lanes within Andromeda which ... | https://en.wikipedia.org/wiki?curid=74331 |
20,464 | In 1943, Walter Baade was the first person to resolve stars in the central region of the Andromeda Galaxy. Baade identified two distinct populations of stars based on their metallicity, naming the young, high-velocity stars in the disk Type I and the older, red stars in the bulge Type II. This nomenclature was subseque... | https://en.wikipedia.org/wiki?curid=74331 |
20,465 | In 1950, radio emission from the Andromeda Galaxy was detected by Hanbury Brown and Cyril Hazard at Jodrell Bank Observatory. The first radio maps of the galaxy were made in the 1950s by John Baldwin and collaborators at the Cambridge Radio Astronomy Group. The core of the Andromeda Galaxy is called 2C 56 in the 2C rad... | https://en.wikipedia.org/wiki?curid=74331 |
20,466 | Observations of linearly polarized radio emission with the Westerbork Synthesis Radio Telescope, the Effelsberg 100-m Radio Telescope, and the Very Large Array revealed ordered magnetic fields aligned along the "10-kpc ring" of gas and star formation. The total magnetic field has a strength of about 0.5 nT, of which 0.... | https://en.wikipedia.org/wiki?curid=74331 |
20,467 | The estimated distance of the Andromeda Galaxy from our own was doubled in 1953 when it was discovered that there is another, dimmer type of Cepheid variable star. In the 1990s, measurements of both standard red giants as well as red clump stars from the "Hipparcos" satellite measurements were used to calibrate the Cep... | https://en.wikipedia.org/wiki?curid=74331 |
20,468 | The Andromeda Galaxy has formed roughly 10 billion years ago from the collision and subsequent merger of smaller protogalaxies. | https://en.wikipedia.org/wiki?curid=74331 |
20,469 | This violent collision formed most of the galaxy's (metal-rich) galactic halo and extended disk. During this epoch, its rate of star formation would have been very high, to the point of becoming a luminous infrared galaxy for roughly 100 million years. Andromeda and the Triangulum Galaxy (M33) had a very close passage ... | https://en.wikipedia.org/wiki?curid=74331 |
20,470 | Over the past 2 billion years, star formation throughout Andromeda's disk is thought to have decreased to the point of near-inactivity. There have been interactions with satellite galaxies such as M32, M110, or others that have already been absorbed by the Andromeda Galaxy. These interactions have formed structures lik... | https://en.wikipedia.org/wiki?curid=74331 |
20,471 | At least four distinct techniques have been used to estimate distances from Earth to the Andromeda Galaxy. In 2003, using the infrared surface brightness fluctuations (I-SBF) and adjusting for the new period-luminosity value and a metallicity correction of −0.2 mag dex in (O/H), an estimate of was derived. A 2004 Cephe... | https://en.wikipedia.org/wiki?curid=74331 |
20,472 | Until 2018, mass estimates for the Andromeda Galaxy's halo (including dark matter) gave a value of approximately , compared to for the Milky Way. This contradicted earlier measurements that seemed to indicate that the Andromeda Galaxy and Milky Way are almost equal in mass. | https://en.wikipedia.org/wiki?curid=74331 |
20,473 | In 2018, the equality of mass was re-established by radio results as approximately . In 2006, the Andromeda Galaxy's spheroid was determined to have a higher stellar density than that of the Milky Way, and its galactic stellar disk was estimated at about twice the diameter of that of the Milky Way. The total mass of th... | https://en.wikipedia.org/wiki?curid=74331 |
20,474 | As of 2019, current calculations based on escape velocity and dynamical mass measurements put the Andromeda Galaxy at , which is only half of the Milky Way's newer mass, calculated in 2019 at . | https://en.wikipedia.org/wiki?curid=74331 |
20,475 | In addition to stars, the Andromeda Galaxy's interstellar medium contains at least in the form of neutral hydrogen, at least as molecular hydrogen (within its innermost 10 kiloparsecs), and of dust. | https://en.wikipedia.org/wiki?curid=74331 |
20,476 | The Andromeda Galaxy is surrounded by a massive halo of hot gas that is estimated to contain half the mass of the stars in the galaxy. The nearly invisible halo stretches about a million light-years from its host galaxy, halfway to our Milky Way Galaxy. Simulations of galaxies indicate the halo formed at the same time ... | https://en.wikipedia.org/wiki?curid=74331 |
20,477 | Compared to the Milky Way, the Andromeda Galaxy appears to have predominantly older stars with ages >7 years. The estimated luminosity of the Andromeda Galaxy, , is about 25% higher than that of our own galaxy. However, the galaxy has a high inclination as seen from Earth, and it's interstellar dust absorbs an unknown ... | https://en.wikipedia.org/wiki?curid=74331 |
20,478 | An estimation done with the help of Spitzer Space Telescope published in 2010 suggests an absolute magnitude (in the blue) of −20.89 (that with a color index of +0.63 translates to an absolute visual magnitude of −21.52, compared to −20.9 for the Milky Way), and a total luminosity in that wavelength of . | https://en.wikipedia.org/wiki?curid=74331 |
20,479 | The rate of star formation in the Milky Way is much higher, with the Andromeda Galaxy producing only about one solar mass per year compared to 3–5 solar masses for the Milky Way. The rate of novae in the Milky Way is also double that of the Andromeda Galaxy. This suggests that the latter once experienced a great star f... | https://en.wikipedia.org/wiki?curid=74331 |
20,480 | According to recent studies, the Andromeda Galaxy lies in what in the Galaxy color–magnitude diagram is known as the "green valley", a region populated by galaxies like the Milky Way in transition from the "blue cloud" (galaxies actively forming new stars) to the "red sequence" (galaxies that lack star formation). Star... | https://en.wikipedia.org/wiki?curid=74331 |
20,481 | Based on its appearance in visible light, the Andromeda Galaxy is classified as an SA(s)b galaxy in the de Vaucouleurs–Sandage extended classification system of spiral galaxies. However, infrared data from the 2MASS survey and the Spitzer Space Telescope showed that Andromeda is actually a barred spiral galaxy, like th... | https://en.wikipedia.org/wiki?curid=74331 |
20,482 | There are various methods used in astronomy in defining the size of a galaxy, and each method can yield different results concerning one another. The most commonly employed is the D standard - the isophote where the photometric brightness of a galaxy in the B-band (445 nm wavelength of light, in the blue part of the vi... | https://en.wikipedia.org/wiki?curid=74331 |
20,483 | A study in 2005 by the Keck telescopes shows the existence of a tenuous sprinkle of stars, or galactic halo, extending outward from the galaxy. The stars in this halo behave differently from the ones in Andromeda's main galactic disc, where they show rather disorganized orbital motions as opposed to the stars in the ma... | https://en.wikipedia.org/wiki?curid=74331 |
20,484 | The galaxy is inclined an estimated 77° relative to Earth (where an angle of 90° would be edge-on). Analysis of the cross-sectional shape of the galaxy appears to demonstrate a pronounced, S-shaped warp, rather than just a flat disk. A possible cause of such a warp could be gravitational interaction with the satellite ... | https://en.wikipedia.org/wiki?curid=74331 |
20,485 | Spectroscopic studies have provided detailed measurements of the rotational velocity of the Andromeda Galaxy as a function of radial distance from the core. The rotational velocity has a maximum value of at from the core, and it has its minimum possibly as low as at from the core. Further out, rotational velocity rises... | https://en.wikipedia.org/wiki?curid=74331 |
20,486 | The spiral arms of the Andromeda Galaxy are outlined by a series of HII regions, first studied in great detail by Walter Baade and described by him as resembling "beads on a string". His studies show two spiral arms that appear to be tightly wound, although they are more widely spaced than in our galaxy. His descriptio... | https://en.wikipedia.org/wiki?curid=74331 |
20,487 | Since the Andromeda Galaxy is seen close to edge-on, it is difficult to study its spiral structure. Rectified images of the galaxy seem to show a fairly normal spiral galaxy, exhibiting two continuous trailing arms that are separated from each other by a minimum of about and that can be followed outward from a distance... | https://en.wikipedia.org/wiki?curid=74331 |
20,488 | The most likely cause of the distortions of the spiral pattern is thought to be interaction with galaxy satellites M32 and M110. This can be seen by the displacement of the neutral hydrogen clouds from the stars. | https://en.wikipedia.org/wiki?curid=74331 |
20,489 | In 1998, images from the European Space Agency's Infrared Space Observatory demonstrated that the overall form of the Andromeda Galaxy may be transitioning into a ring galaxy. The gas and dust within the galaxy are generally formed into several overlapping rings, with a particularly prominent ring formed at a radius of... | https://en.wikipedia.org/wiki?curid=74331 |
20,490 | Later studies with the help of the Spitzer Space Telescope showed how the Andromeda Galaxy's spiral structure in the infrared appears to be composed of two spiral arms that emerge from a central bar and continue beyond the large ring mentioned above. Those arms, however, are not continuous and have a segmented structur... | https://en.wikipedia.org/wiki?curid=74331 |
20,491 | Close examination of the inner region of the Andromeda Galaxy with the same telescope also showed a smaller dust ring that is believed to have been caused by the interaction with M32 more than 200 million years ago. Simulations show that the smaller galaxy passed through the disk of the Andromeda Galaxy along the latte... | https://en.wikipedia.org/wiki?curid=74331 |
20,492 | It is the co-existence of the long-known large ring-like feature in the gas of Messier 31, together with this newly discovered inner ring-like structure, offset from the barycenter, that suggested a nearly head-on collision with the satellite M32, a milder version of the Cartwheel encounter. | https://en.wikipedia.org/wiki?curid=74331 |
20,493 | Studies of the extended halo of the Andromeda Galaxy show that it is roughly comparable to that of the Milky Way, with stars in the halo being generally "metal-poor", and increasingly so with greater distance. This evidence indicates that the two galaxies have followed similar evolutionary paths. They are likely to hav... | https://en.wikipedia.org/wiki?curid=74331 |
20,494 | The Andromeda Galaxy is known to harbor a dense and compact star cluster at its very center. A large telescope creates a visual impression of a star embedded in the more diffuse surrounding bulge. In 1991, the Hubble Space Telescope was used to image the Andromeda Galaxy's inner nucleus. The nucleus consists of two con... | https://en.wikipedia.org/wiki?curid=74331 |
20,495 | It has been proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole. The eccentricity is such that stars linger at the orbital apocenter, creating a concentration of stars. P2 also contains a compact disk of hot, spectra... | https://en.wikipedia.org/wiki?curid=74331 |
20,496 | While at the initial time of its discovery it was hypothesized that the brighter portion of the double nucleus is the remnant of a small galaxy "cannibalized" by the Andromeda Galaxy, this is no longer considered a viable explanation, largely because such a nucleus would have an exceedingly short lifetime due to tidal ... | https://en.wikipedia.org/wiki?curid=74331 |
20,497 | Apparently, by late 1968, no X-rays had been detected from the Andromeda Galaxy. A balloon flight on 20 October 1970, set an upper limit for detectable hard X-rays from the Andromeda Galaxy. The Swift BAT all-sky survey successfully detected hard X-rays coming from a region centered 6 arcseconds away from the galaxy ce... | https://en.wikipedia.org/wiki?curid=74331 |
20,498 | Multiple X-ray sources have since been detected in the Andromeda Galaxy, using observations from the European Space Agency's (ESA) XMM-Newton orbiting observatory. Robin Barnard "et al." hypothesized that these are candidate black holes or neutron stars, which are heating the incoming gas to millions of kelvins and emi... | https://en.wikipedia.org/wiki?curid=74331 |
20,499 | In 2012, a microquasar, a radio burst emanating from a smaller black hole was detected in the Andromeda Galaxy. The progenitor black hole is located near the galactic center and has about 10 . It was discovered through data collected by the European Space Agency's XMM-Newton probe and was subsequently observed by NASA'... | https://en.wikipedia.org/wiki?curid=74331 |
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