text stringlengths 26 3.6k | page_title stringlengths 1 71 | source stringclasses 1
value | token_count int64 10 512 | id stringlengths 2 8 | url stringlengths 31 117 | topic stringclasses 4
values | section stringlengths 4 49 ⌀ | sublist stringclasses 9
values |
|---|---|---|---|---|---|---|---|---|
Types
Dyssomnias – A broad category of sleep disorders characterized by either hypersomnia or insomnia. The three major subcategories include intrinsic (i.e., arising from within the body), extrinsic (secondary to environmental conditions or various pathologic conditions), and disturbances of circadian rhythm.
Insom... | Sleep disorder | Wikipedia | 511 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Dissociative identity disorder
Psychosis (such as Schizophrenia)
Sleeping sickness – a parasitic disease which can be transmitted by the Tsetse fly.
Jet lag disorder – Jet lag disorder is a type of circadian rhythm sleep disorder that results from rapid travel across multiple time zones. Individuals experiencing jet... | Sleep disorder | Wikipedia | 129 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells).
Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during t... | Pollen | Wikipedia | 496 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Formation
Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower.
In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a partially differentiated dermis. As the flower ... | Pollen | Wikipedia | 445 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Except in the case of some submerged aquatic plants, the mature pollen grain has a double wall. The vegetative and generative cells are surrounded by a thin delicate wall of unaltered cellulose called the endospore or intine, and a tough resistant outer cuticularized wall composed largely of sporopollenin called the ex... | Pollen | Wikipedia | 378 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness. They allow shrinking and swelling of the grain caused by changes in moisture content. The process of shrinking the grain is called harmomegathy. Elongated apertures or furrows in the pollen gra... | Pollen | Wikipedia | 460 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Additionally, gymnosperm pollen grains often have air bladders, or vesicles, called sacci. The sacci are not actually balloons, but are sponge-like, and increase the buoyancy of the pollen grain and help keep it aloft in the wind, as most gymnosperms are anemophilous. Pollen can be monosaccate, (containing one saccus) ... | Pollen | Wikipedia | 413 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
When placed on the stigma of a flowering plant, under favorable circumstances, a pollen grain puts forth a pollen tube, which grows down the tissue of the style to the ovary, and makes its way along the placenta, guided by projections or hairs, to the micropyle of an ovule. The nucleus of the tube cell has meanwhile pa... | Pollen | Wikipedia | 453 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Pollen allergies are common in polar and temperate climate zones, where production of pollen is seasonal. In the tropics pollen production varies less by the season, and allergic reactions less.
In northern Europe, common pollens for allergies are those of birch and alder, and in late summer wormwood and different form... | Pollen | Wikipedia | 496 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
In Denmark, decades of rising temperatures cause pollen to appear earlier and in greater amounts, exacerbated by the introduction of new species such as ragweed.
The most efficient way to handle a pollen allergy is by preventing contact with the material. Individuals carrying the ailment may at first believe that they... | Pollen | Wikipedia | 300 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Nutrition
Most major classes of predatory and parasitic arthropods contain species that eat pollen, despite the common perception that bees are the primary pollen-consuming arthropod group. Many Hymenoptera other than bees consume pollen as adults, though only a small number feed on pollen as larvae (including some ant... | Pollen | Wikipedia | 490 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Some species of Heliconius butterflies consume pollen as adults, which appears to be a valuable nutrient source, and these species are more distasteful to predators than the non-pollen consuming species.
Although bats, butterflies, and hummingbirds are not pollen eaters per se, their consumption of nectar in flowers i... | Pollen | Wikipedia | 480 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
In forensic biology, pollen can tell a lot about where a person or object has been, because regions of the world, or even more particular locations such a certain set of bushes, will have a distinctive collection of pollen species. Pollen evidence can also reveal the season in which a particular object picked up the po... | Pollen | Wikipedia | 316 | 46980 | https://en.wikipedia.org/wiki/Pollen | Biology and health sciences | Plant reproduction | null |
Scutum is a small constellation. Its name is Latin for shield, and it was originally named Scutum Sobiescianum by Johannes Hevelius in 1684. Located just south of the celestial equator, its four brightest stars form a narrow diamond shape. It is one of the 88 IAU designated constellations defined in 1922.
History
Sc... | Scutum (constellation) | Wikipedia | 486 | 46981 | https://en.wikipedia.org/wiki/Scutum%20%28constellation%29 | Physical sciences | Other | Astronomy |
UY Scuti is a red supergiant and is also one of the largest stars currently known with a radius over 900 times that of the Sun. RSGC1-F01 is another red supergiant whose radius is over 1,450 times that of the Sun. Scutum contains several clusters of supergiant stars, including RSGC1, Stephenson 2 and RSGC3.
Deep sky o... | Scutum (constellation) | Wikipedia | 322 | 46981 | https://en.wikipedia.org/wiki/Scutum%20%28constellation%29 | Physical sciences | Other | Astronomy |
A buffer solution is a solution where the pH does not change significantly on dilution or if an acid or base is added at constant temperature. Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide var... | Buffer solution | Wikipedia | 506 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
With either definition the buffer capacity for a weak acid HA with dissociation constant Ka can be expressed as
where [H+] is the concentration of hydrogen ions, and is the total concentration of added acid. Kw is the equilibrium constant for self-ionization of water, equal to 1.0. Note that in solution H+ exists as ... | Buffer solution | Wikipedia | 441 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
Applications of buffers
The pH of a solution containing a buffering agent can only vary within a narrow range, regardless of what else may be present in the solution. In biological systems this is an essential condition for enzymes to function correctly. For example, in human blood a mixture of carbonic acid (HCO) and ... | Buffer solution | Wikipedia | 507 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
"Universal" buffer mixtures
By combining substances with pKa values differing by only two or less and adjusting the pH, a wide range of buffers can be obtained. Citric acid is a useful component of a buffer mixture because it has three pKa values, separated by less than two. The buffer range can be extended by adding o... | Buffer solution | Wikipedia | 420 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
This shows that when the acid dissociates, equal amounts of hydrogen ion and anion are produced. The equilibrium concentrations of these three components can be calculated in an ICE table (ICE standing for "initial, change, equilibrium").
{| class="wikitable"
|+ ICE table for a monoprotic acid
|-
!
! [HA] !! [A−] !! [H... | Buffer solution | Wikipedia | 389 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
Polyprotic acids are acids that can lose more than one proton. The constant for dissociation of the first proton may be denoted as Ka1, and the constants for dissociation of successive protons as Ka2, etc. Citric acid is an example of a polyprotic acid H3A, as it can lose three protons.
{| class="wikitable" style="widt... | Buffer solution | Wikipedia | 381 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
N.B. The numbering of cumulative, overall constants is the reverse of the numbering of the stepwise, dissociation constants.
{| class="wikitable"
|+ Relationship between cumulative association constant (β) values and stepwise dissociation constant (K) values for a tribasic acid.
! Equilibrium!! Relationship
|-
| A3− + ... | Buffer solution | Wikipedia | 175 | 46999 | https://en.wikipedia.org/wiki/Buffer%20solution | Physical sciences | Concepts | Chemistry |
In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equili... | Arrhenius equation | Wikipedia | 394 | 47011 | https://en.wikipedia.org/wiki/Arrhenius%20equation | Physical sciences | Kinetics | Chemistry |
The unit of the pre-exponential factor are identical to those of the rate constant and will vary depending on the order of the reaction. If the reaction is first order it has the unit s−1, and for that reason it is often called the frequency factor or attempt frequency of the reaction. Most simply, is the number of c... | Arrhenius equation | Wikipedia | 506 | 47011 | https://en.wikipedia.org/wiki/Arrhenius%20equation | Physical sciences | Kinetics | Chemistry |
So, when a reaction has a rate constant obeying the Arrhenius equation, a plot of ln k versus T−1 gives a straight line, whose slope and intercept can be used to determine Ea and A respectively. This procedure is common in experimental chemical kinetics. The activation energy is simply obtained by multiplying by (−R) t... | Arrhenius equation | Wikipedia | 447 | 47011 | https://en.wikipedia.org/wiki/Arrhenius%20equation | Physical sciences | Kinetics | Chemistry |
One approach is the collision theory of chemical reactions, developed by Max Trautz and William Lewis in the years 1916–18. In this theory, molecules are supposed to react if they collide with a relative kinetic energy along their line of centers that exceeds Ea. The number of binary collisions between two unlike molec... | Arrhenius equation | Wikipedia | 438 | 47011 | https://en.wikipedia.org/wiki/Arrhenius%20equation | Physical sciences | Kinetics | Chemistry |
Limitations of the idea of Arrhenius activation energy
Both the Arrhenius activation energy and the rate constant k are experimentally determined, and represent macroscopic reaction-specific parameters that are not simply related to threshold energies and the success of individual collisions at the molecular level. Co... | Arrhenius equation | Wikipedia | 372 | 47011 | https://en.wikipedia.org/wiki/Arrhenius%20equation | Physical sciences | Kinetics | Chemistry |
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a filament that is heated until it glows. The filament is enclosed in a glass bulb that is either evacuated or filled with inert gas to protect the filament from oxidation. Electric current is supplied to the filament by... | Incandescent light bulb | Wikipedia | 435 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
History
Historians Robert Friedel and Paul Israel list inventors of incandescent lamps prior to Joseph Swan and Thomas Edison of General Electric. They conclude that Edison's version was the first practical implementation, able to outstrip the others because of a combination of four factors: an effective incandescent m... | Incandescent light bulb | Wikipedia | 509 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
In 1835, James Bowman Lindsay demonstrated a constant electric light at a public meeting in Dundee, Scotland. He stated that he could "read a book at a distance of one and a half feet". However he did not develop the electric light any further.
In 1838, Belgian lithographer Marcellin Jobard invented an incandescent li... | Incandescent light bulb | Wikipedia | 458 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
On 24 July 1874, a Canadian patent was filed by Henry Woodward and Mathew Evans for a lamp consisting of carbon rods mounted in a nitrogen-filled glass cylinder. They were unsuccessful at commercializing their lamp, and sold rights to their patent to Thomas Edison in 1879. (Edison needed ownership of the novel claim of... | Incandescent light bulb | Wikipedia | 448 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
With the help of Charles Stearn, an expert on vacuum pumps, in 1878, Swan developed a method of processing that avoided the early bulb blackening. This received a British Patent in 1880. On 18 December 1878, a lamp using a slender carbon rod was shown at a meeting of the Newcastle Chemical Society, and Swan gave a work... | Incandescent light bulb | Wikipedia | 376 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Thomas Edison began serious research into developing a practical incandescent lamp in 1878. Edison filed his first patent application for "Improvement in Electric Lights" on 14 October 1878. After many experiments, first with carbon in the early 1880s and then with platinum and other metals, in the end Edison returned ... | Incandescent light bulb | Wikipedia | 506 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
In Britain, the Edison and Swan companies merged into the Edison and Swan United Electric Company (later known as Ediswan, and ultimately incorporated into Thorn Lighting Ltd). Edison was initially against this combination, but Edison was eventually forced to cooperate and the merger was made. Eventually, Edison acquir... | Incandescent light bulb | Wikipedia | 368 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
US575002A patent on 01.Dec.1897 to Alexander Lodyguine (Lodygin, Russia) describes filament made of rare metals, amongst them was tungsten. Lodygin invented a process where rare metals such as tungsten can be chemically treated and heat-vaporized onto an electrically heated thread-like wire (platinum, carbon, gold) act... | Incandescent light bulb | Wikipedia | 472 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
In 1906, William D. Coolidge developed a method of making "ductile tungsten" from sintered tungsten which could be made into filaments while working for General Electric Company. By 1911 General Electric had begun selling incandescent light bulbs with ductile tungsten wire.
In 1913, Irving Langmuir found that filling ... | Incandescent light bulb | Wikipedia | 418 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Consumption of incandescent light bulbs grew rapidly in the US. In 1885, an estimated 300,000 general lighting service lamps were sold, all with carbon filaments. When tungsten filaments were introduced, about 50 million lamp sockets existed in the US. In 1914, 88.5 million lamps were used, (only 15% with carbon filame... | Incandescent light bulb | Wikipedia | 414 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Light sources such as fluorescent lamps, high-intensity discharge lamps and LED lamps have higher luminous efficiency. These devices produce light by luminescence. Their light has bands of characteristic wavelengths, without the "tail" of invisible infrared emissions, instead of the continuous spectrum produced by a th... | Incandescent light bulb | Wikipedia | 487 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Objections to banning the use of incandescent light bulbs include the higher initial cost of alternatives and lower quality of light of fluorescent lamps. Some people have concerns about the health effects of fluorescent lamps.
Efforts to improve efficacy
Some research has been carried out to improve the efficacy of ... | Incandescent light bulb | Wikipedia | 455 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
An electric current heats the filament to typically , well below tungsten's melting point of . Filament temperatures depend on the filament type, shape, size, and amount of current drawn. The heated filament emits light that approximates a continuous spectrum. The useful part of the emitted energy is visible light, but... | Incandescent light bulb | Wikipedia | 376 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
The gas reduces evaporation of the filament, but the fill must be chosen carefully to avoid introducing significant heat losses. For these properties, chemical inertness and high atomic or molecular weight is desirable. The presence of gas molecules knocks the liberated tungsten atoms back to the filament, reducing its... | Incandescent light bulb | Wikipedia | 506 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
The gas layer close to the filament (called the Langmuir layer) is stagnant, with heat transfer occurring only by conduction. Only at some distance does convection occur to carry heat to the bulb's envelope.
The orientation of the filament influences efficiency. Gas flow parallel to the filament, e.g., a vertically or... | Incandescent light bulb | Wikipedia | 428 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
The Ribbon Machine works by passing a continuous ribbon of glass along a conveyor belt, heated in a furnace, and then blown by precisely aligned air nozzles through holes in the conveyor belt into molds. Thus the glass bulbs or envelopes are created. A typical machine of this sort can produce anywhere from 50,000 to 12... | Incandescent light bulb | Wikipedia | 439 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Metal filaments were tried in 1897 and started to displace carbon starting around 1904. Tungsten has the highest available melting point, but brittleness was a big obstacle. By 1910, a process was developed by William D. Coolidge at General Electric for production of a ductile form of tungsten. The process required pre... | Incandescent light bulb | Wikipedia | 489 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Electrical filaments are also used in hot cathodes of fluorescent lamps and vacuum tubes as a source of electrons or in vacuum tubes to heat an electron-emitting electrode. When used as a source of electrons, they may have a special coating that increases electron production.
Reducing filament evaporation
During ordin... | Incandescent light bulb | Wikipedia | 373 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Filament notching is due to uneven evaporation of the filament. Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. Since filament resistance is highly temperature-dependent, spots wi... | Incandescent light bulb | Wikipedia | 453 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
A very small amount of water vapor inside a light bulb can significantly increase lamp darkening. Water vapor dissociates into hydrogen and oxygen at the hot filament. The oxygen attacks the tungsten metal, and the resulting tungsten oxide particles travel to cooler parts of the lamp. Hydrogen from water vapor reduces ... | Incandescent light bulb | Wikipedia | 489 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Power
Incandescent lamps are nearly pure resistive loads with a power factor of 1. Unlike discharge lamps or LED lamps, the power consumed is equal to the apparent power in the circuit. Incandescent light bulbs are usually marketed according to the electrical power consumed. This depends mainly on the operating resista... | Incandescent light bulb | Wikipedia | 486 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
A hot glass bulb may fracture on contact with cold objects. When the glass envelope breaks, the bulb implodes, exposing the filament to ambient air. The air then usually destroys the hot filament through oxidation.
Bulb shapes
Bulb shape and size designations are given in national standards.
Some designations are... | Incandescent light bulb | Wikipedia | 413 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Parabolic aluminized reflector (PAR)
Parabolic aluminized reflector (PAR) bulbs control light more precisely. They produce about four times the concentrated light intensity of general service (A), and are used in recessed and track lighting. Weatherproof casings are available for outdoor spot and flood fixtures.
120 V ... | Incandescent light bulb | Wikipedia | 475 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Contacts in the lightbulb socket allow the electric current to pass through the base to the filament. The socket provides electrical connections and mechanical support, and allows changing the lamp when it burns out.
Light output and lifetime
Incandescent lamps are very sensitive to changes in the supply voltage. The... | Incandescent light bulb | Wikipedia | 498 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Lamps of the same power rating but designed for different voltages have different luminous efficacy. For example, a 100-watt, 1000 hour, 120-volt lamp will produce about 17.1 lumens per watt. A similar lamp designed for 230 V would produce only around 12.8 lumens per watt, and one designed for 30 volts (train lighting)... | Incandescent light bulb | Wikipedia | 308 | 47139 | https://en.wikipedia.org/wiki/Incandescent%20light%20bulb | Technology | Electricity generation and distribution | null |
Vesta (minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, the virgin goddess of home and hearth from Roman mythology.
Vesta is thought to ... | 4 Vesta | Wikipedia | 356 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Heinrich Olbers discovered Pallas in 1802, the year after the discovery of Ceres. He proposed that the two objects were the remnants of a destroyed planet. He sent a letter with his proposal to the British astronomer William Herschel, suggesting that a search near the locations where the orbits of Ceres and Pallas in... | 4 Vesta | Wikipedia | 422 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Upon its discovery, Vesta was, like Ceres, Pallas, and Juno before it, classified as a planet and given a planetary symbol. The symbol represented the altar of Vesta with its sacred fire and was designed by Gauss. In Gauss's conception, now obsolete, this was drawn . His form is in the pipeline for Unicode 17.0 as U+1F... | 4 Vesta | Wikipedia | 426 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Early estimates of the diameter of Vesta ranged from in 1825, to . E.C. Pickering produced an estimated diameter of in 1879, which is close to the modern value for the mean diameter, but the subsequent estimates ranged from a low of up to a high of during the next century. The measured estimates were based on photo... | 4 Vesta | Wikipedia | 494 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Vesta's rotation is relatively fast for an asteroid (5.342 h) and prograde, with the north pole pointing in the direction of right ascension 20 h 32 min, declination +48° (in the constellation Cygnus) with an uncertainty of about 10°. This gives an axial tilt of 29°.
Coordinate systems
Two longitudinal coordinate syst... | 4 Vesta | Wikipedia | 505 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Vesta's shape is close to a gravitationally relaxed oblate spheroid, but the large concavity and protrusion at the southern pole (see 'Surface features' below) combined with a mass less than precluded Vesta from automatically being considered a dwarf planet under International Astronomical Union (IAU) Resolution XXVI ... | 4 Vesta | Wikipedia | 227 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
The most prominent of these surface features are two enormous impact basins, the -wide Rheasilvia, centered near the south pole; and the wide Veneneia. The Rheasilvia impact basin is younger and overlies the Veneneia. The Dawn science team named the younger, more prominent crater Rheasilvia, after the mother of Romulu... | 4 Vesta | Wikipedia | 509 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
"Snowman craters"
The "snowman craters" are a group of three adjacent craters in Vesta's northern hemisphere. Their official names, from largest to smallest (west to east), are Marcia, Calpurnia, and Minucia. Marcia is the youngest and cross-cuts Calpurnia. Minucia is the oldest.
Troughs
The majority of the equatorial... | 4 Vesta | Wikipedia | 305 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Surface composition
Compositional information from the visible and infrared spectrometer (VIR), gamma-ray and neutron detector (GRaND), and framing camera (FC), all indicate that the majority of the surface composition of Vesta is consistent with the composition of the howardite, eucrite, and diogenite meteorites. The ... | 4 Vesta | Wikipedia | 494 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
A large collection of potential samples from Vesta is accessible to scientists, in the form of over 1200 HED meteorites (Vestan achondrites), giving insight into Vesta's geologic history and structure. NASA Infrared Telescope Facility (NASA IRTF) studies of asteroid suggest that it originated from deeper within Vesta ... | 4 Vesta | Wikipedia | 404 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Regolith
Vesta's surface is covered by regolith distinct from that found on the Moon or asteroids such as Itokawa. This is because space weathering acts differently. Vesta's surface shows no significant trace of nanophase iron because the impact speeds on Vesta are too low to make rock melting and vaporization an appre... | 4 Vesta | Wikipedia | 295 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
In 1981, a proposal for an asteroid mission was submitted to the European Space Agency (ESA). Named the Asteroidal Gravity Optical and Radar Analysis (AGORA), this spacecraft was to launch some time in 1990–1994 and perform two flybys of large asteroids. The preferred target for this mission was Vesta. AGORA would reac... | 4 Vesta | Wikipedia | 491 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
NASA/DLR released imagery and summary information from a survey orbit, two high-altitude orbits (60–70 m/pixel) and a low-altitude mapping orbit (20 m/pixel), including digital terrain models, videos and atlases. Scientists also used Dawn to calculate Vesta's precise mass and gravity field. The subsequent determination... | 4 Vesta | Wikipedia | 448 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
2012–2013
Vesta was at opposition again on 9 December 2012. According to Sky and Telescope magazine, this year Vesta came within about 6 degrees of 1 Ceres during the winter of 2012 and spring 2013. Vesta orbits the Sun in 3.63 years and Ceres in 4.6 years, so every 17.4 years Vesta overtakes Ceres (the previous overta... | 4 Vesta | Wikipedia | 135 | 47200 | https://en.wikipedia.org/wiki/4%20Vesta | Physical sciences | Solar System | Astronomy |
Pallas (minor-planet designation: 2 Pallas) is the third-largest asteroid in the Solar System by volume and mass. It is the second asteroid to have been discovered, after Ceres, and is likely a remnant protoplanet. Like Ceres, it is believed to have a mineral composition similar to carbonaceous chondrite meteorites, th... | 2 Pallas | Wikipedia | 462 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
Discovery
On the night of 5 April 1779, Charles Messier recorded Pallas on a star chart he used to track the path of a comet, now known as C/1779 A1 (Bode), that he observed in the spring of 1779, but apparently assumed it was nothing more than a star.
In 1801, the astronomer Giuseppe Piazzi discovered an object whic... | 2 Pallas | Wikipedia | 487 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
Pallas has been observed occulting stars several times, including the best-observed of all asteroid occultation events, by 140 observers on 29 May 1983. These measurements resulted in the first accurate calculation of its diameter.
After an occultation on 29 May 1979, the discovery of a possible tiny satellite with a d... | 2 Pallas | Wikipedia | 444 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
Pallas has unusual dynamic parameters for such a large body. Its orbit is highly inclined and moderately eccentric, despite being at the same distance from the Sun as the central part of the asteroid belt. Furthermore, Pallas has a very high axial tilt of 84°, with its north pole pointing towards ecliptic coordinates (... | 2 Pallas | Wikipedia | 505 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
Pallas is a B-type asteroid. Based on spectroscopic observations, the primary component of the material on Pallas's surface is a silicate containing little iron and water. Minerals of this type include olivine and pyroxene, which are found in CM chondrules. The surface composition of Pallas is very similar to the Renaz... | 2 Pallas | Wikipedia | 449 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
Pallas probably has a quite homogeneous interior. The close match between Pallas and CM chondrites suggests that they formed in the same era and that the interior of Pallas never reached the temperature (≈820 K) needed to dehydrate silicates, which would be necessary to differentiate a dry silicate core beneath a hydra... | 2 Pallas | Wikipedia | 469 | 47262 | https://en.wikipedia.org/wiki/2%20Pallas | Physical sciences | Solar System | Astronomy |
243 Ida is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner aste... | 243 Ida | Wikipedia | 506 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Ida's reflection spectrum was measured on 16 September 1980 by astronomers David J. Tholen and Edward F. Tedesco as part of the eight-color asteroid survey (ECAS). Its spectrum matched those of the asteroids in the S-type classification. Many observations of Ida were made in early 1993 by the US Naval Observatory in Fl... | 243 Ida | Wikipedia | 481 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Ida is classified as an S-type asteroid based on ground-based spectroscopic measurements. The composition of S-types was uncertain before the Galileo flybys, but was interpreted to be either of two minerals found in meteorites that had fallen to the Earth: ordinary chondrite (OC) and stony-iron. Estimates of Ida's dens... | 243 Ida | Wikipedia | 445 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Ida is a distinctly elongated asteroid, with an irregular surface. Ida is 2.35 times as long as it is wide, and a "waist" separates it into two geologically dissimilar halves. This constricted shape is consistent with Ida being made of two large, solid components, with loose debris filling the gap between them. However... | 243 Ida | Wikipedia | 512 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Structures
Several major structures mark Ida's surface. The asteroid appears to be split into two halves, here referred to as region 1 and region 2, connected by a "waist". This feature may have been filled in by debris, or blasted out of the asteroid by impacts.
Region 1 of Ida contains two major structures. One is ... | 243 Ida | Wikipedia | 442 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
The craters are simple in structure: bowl-shaped with no flat bottoms and no central peaks. They are distributed evenly around Ida, except for a protrusion north of crater Choukoutien which is smoother and less cratered. The ejecta excavated by impacts is deposited differently on Ida than on planets because of its rapi... | 243 Ida | Wikipedia | 426 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Ida rotates in the retrograde direction with a rotation period of 4.63 hours (roughly 5 hours). The calculated maximum moment of inertia of a uniformly dense object the same shape as Ida coincides with the spin axis of the asteroid. This suggests that there are no major variations of density within the asteroid. Ida's ... | 243 Ida | Wikipedia | 489 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
Physical characteristics
Dactyl is an "egg-shaped" but "remarkably spherical" object measuring . It is oriented with its longest axis pointing towards Ida. Like Ida, Dactyl's surface exhibits saturation cratering. It is marked by more than a dozen craters with a diameter greater than , indicating that the moon has suf... | 243 Ida | Wikipedia | 475 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
If in a circular orbit at the distance at which it was seen, Dactyl's orbital period would be about 20 hours. Its orbital speed is roughly , "about the speed of a fast run or a slowly thrown baseball".
Age and origin
Dactyl may have originated at the same time as Ida, from the disruption of the Koronis parent body. H... | 243 Ida | Wikipedia | 127 | 47263 | https://en.wikipedia.org/wiki/243%20Ida | Physical sciences | Solar System | Astronomy |
The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets. The identified objects are of many sizes, but much smaller t... | Asteroid belt | Wikipedia | 376 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
The asteroid belt formed from the primordial solar nebula as a group of planetesimals, the smaller precursors of the protoplanets. However, between Mars and Jupiter gravitational perturbations from Jupiter disrupted their accretion into a planet, imparting excess kinetic energy which shattered colliding planetesimals a... | Asteroid belt | Wikipedia | 471 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
On January 1, 1801, Giuseppe Piazzi, chairman of astronomy at the University of Palermo, Sicily, found a tiny moving object in an orbit with exactly the radius predicted by this pattern. He dubbed it "Ceres", after the Roman goddess of the harvest and patron of Sicily. Piazzi initially believed it to be a comet, but it... | Asteroid belt | Wikipedia | 451 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Despite Herschel's coinage, for several decades it remained common practice to refer to these objects as planets and to prefix their names with numbers representing their sequence of discovery: 1 Ceres, 2 Pallas, 3 Juno, 4 Vesta. In 1845, though, the astronomer Karl Ludwig Hencke detected a fifth object (5 Astraea) and... | Asteroid belt | Wikipedia | 480 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
On 22 January 2014, European Space Agency (ESA) scientists reported the detection, for the first definitive time, of water vapor on Ceres, the largest object in the asteroid belt. The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding was unexpected because comets, not... | Asteroid belt | Wikipedia | 411 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Planetesimals within the region that would become the asteroid belt were strongly perturbed by Jupiter's gravity. Orbital resonances occurred where the orbital period of an object in the belt formed an integer fraction of the orbital period of Jupiter, perturbing the object into a different orbit; the region lying betw... | Asteroid belt | Wikipedia | 509 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
The 4:1 orbital resonance with Jupiter, at a radius 2.06 astronomical units (AUs), can be considered the inner boundary of the asteroid belt. Perturbations by Jupiter send bodies straying there into unstable orbits. Most bodies formed within the radius of this gap were swept up by Mars (which has an aphelion at 1.67 AU... | Asteroid belt | Wikipedia | 479 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
The absolute magnitudes of most of the known asteroids are between 11 and 19, with the median at about 16. On average the distance between the asteroids is about , although this varies among asteroid families and smaller undetected asteroids might be even closer. The total mass of the asteroid belt is estimated to be ... | Asteroid belt | Wikipedia | 477 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
M-type (metal-rich) asteroids are typically found in the middle of the main belt, and they make up much of the remainder of the total population. Their spectra resemble that of iron-nickel. Some are believed to have formed from the metallic cores of differentiated progenitor bodies that were disrupted through collision... | Asteroid belt | Wikipedia | 463 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Several otherwise unremarkable bodies in the outer belt show cometary activity. Because their orbits cannot be explained through the capture of classical comets, many of the outer asteroids are thought to be icy, with the ice occasionally exposed to sublimation through small impacts. Main-belt comets may have been a m... | Asteroid belt | Wikipedia | 402 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
When the mean orbital period of an asteroid is an integer fraction of the orbital period of Jupiter, a mean-motion resonance with the gas giant is created that is sufficient to perturb an asteroid to new orbital elements. Primordial asteroids entered these gaps because of the migration of Jupiter's orbit. Subsequently,... | Asteroid belt | Wikipedia | 364 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
The combination of this fine asteroid dust, as well as ejected cometary material, produces the zodiacal light. This faint auroral glow can be viewed at night extending from the direction of the Sun along the plane of the ecliptic. Asteroid particles that produce visible zodiacal light average about 40 μm in radius. The... | Asteroid belt | Wikipedia | 386 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Some of the most prominent families in the asteroid belt (in order of increasing semi-major axes) are the Flora, Eunomia, Koronis, Eos, and Themis families. The Flora family, one of the largest with more than 800 known members, may have formed from a collision less than 1 billion years ago.
The largest asteroid to be a... | Asteroid belt | Wikipedia | 490 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Another high-inclination group in the inner part of the asteroid belt is the Phocaea family. These are composed primarily of S-type asteroids, whereas the neighboring Hungaria family includes some E-types. The Phocaea family orbit between 2.25 and 2.5 AU from the Sun.
Skirting the outer edge of the asteroid belt is th... | Asteroid belt | Wikipedia | 474 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Most main belt asteroids imaged to date have come from brief flyby opportunities by probes headed for other targets. Only the Dawn mission has studied main belt asteroids for a protracted period in orbit. The Galileo spacecraft imaged 951 Gaspra in 1991 and 243 Ida in 1993, then NEAR imaged 253 Mathilde in 1997 and lan... | Asteroid belt | Wikipedia | 233 | 47264 | https://en.wikipedia.org/wiki/Asteroid%20belt | Physical sciences | Solar System | null |
Sponges or sea sponges are primarily marine invertebrates of the metazoan phylum Porifera ( ; meaning 'pore bearer'), a basal animal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and are one of the most ancient members of macrobenthos, with many historical sp... | Sponge | Wikipedia | 353 | 47271 | https://en.wikipedia.org/wiki/Sponge | Biology and health sciences | Porifera | null |
Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs. Some of them are radially symmetrical, but most are asymmetrical. The shapes of their bodies are adapted for maximal efficiency of water f... | Sponge | Wikipedia | 496 | 47271 | https://en.wikipedia.org/wiki/Sponge | Biology and health sciences | Porifera | null |
Although most of the approximately 5,000–10,000 known species of sponges feed on bacteria and other microscopic food in the water, some host photosynthesizing microorganisms as endosymbionts, and these alliances often produce more food and oxygen than they consume. A few species of sponges that live in food-poor enviro... | Sponge | Wikipedia | 476 | 47271 | https://en.wikipedia.org/wiki/Sponge | Biology and health sciences | Porifera | null |
Even if a few sponges are able to produce mucus – which acts as a microbial barrier in all other animals – no sponge with the ability to secrete a functional mucus layer has been recorded. Without such a mucus layer their living tissue is covered by a layer of microbial symbionts, which can contribute up to 40–50% of t... | Sponge | Wikipedia | 497 | 47271 | https://en.wikipedia.org/wiki/Sponge | Biology and health sciences | Porifera | null |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.