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Conjunctivitis, also known as pink eye or Madras eye, is inflammation of the conjunctiva and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. The affected eye may have increased tears or be "stuck shut" in the morning. Swelling of the sclera ... | Conjunctivitis | Wikipedia | 500 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Approximately 80% of cases of conjunctivitis in adults and less than 20% in children are due to viruses, with 65% to 90% of these cases being attributed to adenoviruses.
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Other associated signs may... | Conjunctivitis | Wikipedia | 306 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Bacteria are responsible for approximately 70% of conjunctivitis in children and less than 20% of cases in adults. Common bacteria responsible for bacterial conjunctivitis are Staphylococcus including Staph aureus, Streptococcus such as strep pneumoniae, Haemophilus species and Moraxella catarrhalis. Less commonly, Chl... | Conjunctivitis | Wikipedia | 459 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Chemical
Chemical eye injury may result when an acidic or alkaline substance gets in the eye. Alkali burns are typically worse than acidic burns. Mild burns produce conjunctivitis, while more severe burns may cause the cornea to turn white. Litmus paper may be used to test for chemical causes. When a chemical cause ha... | Conjunctivitis | Wikipedia | 496 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Viral
Adenoviruses are the most common cause of viral conjunctivitis (adenoviral keratoconjunctivitis). Herpetic keratoconjunctivitis, caused by herpes simplex viruses, can be serious and requires treatment with aciclovir. Acute hemorrhagic conjunctivitis is a highly contagious disease caused by one of two enterovirus... | Conjunctivitis | Wikipedia | 498 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Although conjunctival scrapes for cytology can be useful in detecting chlamydial and fungal infections, allergies, and dysplasia, they are rarely done because of the cost and the general dearth of laboratory staff experienced in handling ocular specimens. Conjunctival incisional biopsy is occasionally done when granulo... | Conjunctivitis | Wikipedia | 450 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
A more comprehensive differential diagnosis for the red or painful eye includes:
Corneal abrasion
Subconjunctival hemorrhage
Pinguecula
Blepharitis
Dacryocystitis
Keratoconjunctivitis sicca (dry eye)
Keratitis
Herpes simplex
Herpes zoster
Episcleritis – an inflammatory condition that produces a similar appear... | Conjunctivitis | Wikipedia | 401 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Bacterial
Bacterial conjunctivitis usually resolves without treatment. Topical antibiotics may be needed only if no improvement is observed after 3 days. No serious effects were noted either with or without treatment. Because antibiotics do speed healing in bacterial conjunctivitis, their use may be considered. Antibi... | Conjunctivitis | Wikipedia | 499 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
History
An adenovirus was first isolated by Rowe et al. in 1953. Two years later, Jawetz et al. published on epidemic keratoconjunctivitis. "Madras eye" is a colloquial term that has been used in India for the disease.
Outbreak in Pakistan
In September 2023, a significant outbreak of conjunctivitis occurred in Pakis... | Conjunctivitis | Wikipedia | 243 | 44410 | https://en.wikipedia.org/wiki/Conjunctivitis | Biology and health sciences | Infectious diseases by site | Health | vital_articles |
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of sediments, ie. mineral or organic particles, at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock ... | Sedimentary rock | Wikipedia | 473 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Sedimentary rocks can be subdivided into four groups based on the processes responsible for their formation: clastic sedimentary rocks, biochemical (biogenic) sedimentary rocks, chemical sedimentary rocks, and a fourth category for "other" sedimentary rocks formed by impacts, volcanism, and other minor processes.
Clas... | Sedimentary rock | Wikipedia | 497 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Quartz sandstones have >90% quartz grains
Feldspathic sandstones have <90% quartz grains and more feldspar grains than lithic grains
Lithic sandstones have <90% quartz grains and more lithic grains than feldspar grains
Abundance of muddy matrix material between sand grains
When sand-sized particles are deposited, th... | Sedimentary rock | Wikipedia | 434 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue. Examples include:
Most types of limestone are formed from the calcareous skeletons of organisms such as corals, mollusks, and foraminifera.
Coal, formed from vegetation that has removed carbon from ... | Sedimentary rock | Wikipedia | 222 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Alternatively, sedimentary rocks can be subdivided into compositional groups based on their mineralogy:
Siliciclastic sedimentary rocks, are dominantly composed of silicate minerals. The sediment that makes up these rocks was transported as bed load, suspended load, or by sediment gravity flows. Siliciclastic sediment... | Sedimentary rock | Wikipedia | 508 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
As sediments accumulate in a depositional environment, older sediments are buried by younger sediments, and they undergo diagenesis. Diagenesis includes all the chemical, physical, and biological changes, exclusive of surface weathering, undergone by a sediment after its initial deposition. This includes compaction and... | Sedimentary rock | Wikipedia | 512 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Properties
Color
The color of a sedimentary rock is often mostly determined by iron, an element with two major oxides: iron(II) oxide and iron(III) oxide. Iron(II) oxide (FeO) only forms under low oxygen (anoxic) circumstances and gives the rock a grey or greenish colour. Iron(III) oxide (Fe2O3) in a richer oxygen en... | Sedimentary rock | Wikipedia | 350 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
The 3D orientation of the clasts is called the fabric of the rock. The size and form of clasts can be used to determine the velocity and direction of current in the sedimentary environment that moved the clasts from their origin; fine, calcareous mud only settles in quiet water while gravel and larger clasts are moved ... | Sedimentary rock | Wikipedia | 508 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Carbonate rocks predominantly consist of carbonate minerals such as calcite, aragonite or dolomite. Both the cement and the clasts (including fossils and ooids) of a carbonate sedimentary rock usually consist of carbonate minerals. The mineralogy of a clastic rock is determined by the material supplied by the source ar... | Sedimentary rock | Wikipedia | 449 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
As a part of a sedimentary rock, fossils undergo the same diagenetic processes as does the host rock. For example, a shell consisting of calcite can dissolve while a cement of silica then fills the cavity. In the same way, precipitating minerals can fill cavities formerly occupied by blood vessels, vascular tissue or o... | Sedimentary rock | Wikipedia | 490 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
The opposite of cross-bedding is parallel lamination, where all sedimentary layering is parallel. Differences in laminations are generally caused by cyclic changes in the sediment supply, caused, for example, by seasonal changes in rainfall, temperature or biochemical activity. Laminae that represent seasonal changes (... | Sedimentary rock | Wikipedia | 411 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Organic materials in a sediment can leave more traces than just fossils. Preserved tracks and burrows are examples of trace fossils (also called ichnofossils). Such traces are relatively rare. Most trace fossils are burrows of molluscs or arthropods. This burrowing is called bioturbation by sedimentologists. It can be ... | Sedimentary rock | Wikipedia | 505 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Sedimentary dykes can also be formed in a cold climate where the soil is permanently frozen during a large part of the year. Frost weathering can form cracks in the soil that fill with rubble from above. Such structures can be used as climate indicators as well as way up structures.
Density contrasts can also cause sm... | Sedimentary rock | Wikipedia | 502 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
In deep marine environments, the water current working the sea bottom is small. Only fine particles can be transported to such places. Typically sediments depositing on the ocean floor are fine clay or small skeletons of micro-organisms. At 4 km depth, the solubility of carbonates increases dramatically (the depth zone... | Sedimentary rock | Wikipedia | 510 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Aeolian deposits can be quite striking. The depositional environment of the Touchet Formation, located in the Northwestern United States, had intervening periods of aridity which resulted in a series of rhythmite layers. Erosional cracks were later infilled with layers of soil material, especially from aeolian processe... | Sedimentary rock | Wikipedia | 469 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
The situation in which coastlines move in the direction of the continent is called transgression. In the case of transgression, deeper marine facies are deposited over shallower facies, a succession called onlap. Regression is the situation in which a coastline moves in the direction of the sea. With regression, shallo... | Sedimentary rock | Wikipedia | 500 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
A third type of basin exists along convergent plate boundaries – places where one tectonic plate moves under another into the asthenosphere. The subducting plate bends and forms a fore-arc basin in front of the overriding plate – an elongated, deep asymmetric basin. Fore-arc basins are filled with deep marine deposits ... | Sedimentary rock | Wikipedia | 493 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Sedimentation rates
The rate at which sediment is deposited differs depending on the location. A channel in a tidal flat can see the deposition of a few metres of sediment in one day, while on the deep ocean floor each year only a few millimetres of sediment accumulate. A distinction can be made between normal sediment... | Sedimentary rock | Wikipedia | 509 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Provenance is the reconstruction of the origin of sediments. All rock exposed at Earth's surface is subjected to physical or chemical weathering and broken down into finer grained sediment. All three types of rocks (igneous, sedimentary and metamorphic rocks) can be the source of sedimentary detritus. The purpose of se... | Sedimentary rock | Wikipedia | 98 | 44412 | https://en.wikipedia.org/wiki/Sedimentary%20rock | Physical sciences | Petrology | null | vital_articles |
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causing profound physical or chemical changes. During this process, the rock remains... | Metamorphic rock | Wikipedia | 478 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Hutton also speculated that pressure was important in metamorphism. This hypothesis was tested by his friend, James Hall, who sealed chalk into a makeshift pressure vessel constructed from a cannon barrel and heated it in an iron foundry furnace. Hall found that this produced a material strongly resembling marble, rath... | Metamorphic rock | Wikipedia | 446 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Textural changes
The change in the particle size of the rock during the process of metamorphism is called recrystallization. For instance, the small calcite crystals in the sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble. In metamorphosed sandstone, recrystallization of t... | Metamorphic rock | Wikipedia | 486 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Many kinds of metamorphic rocks show a distinctive layering called foliation (derived from the Latin word folia, meaning "leaves"). Foliation develops when a rock is being shortened along one axis during recrystallization. This causes crystals of platy minerals, such as mica and chlorite, to become rotated such that th... | Metamorphic rock | Wikipedia | 499 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Under the British Geological Survey's classification system, if all that can be determined about the protolith is its general type, such as sedimentary or volcanic, the classification is based on the mineral mode (the volume percentages of different minerals in the rock). Metasedimentary rocks are divided into carbonat... | Metamorphic rock | Wikipedia | 504 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Special classifications exist for metamorphic rocks with a volcaniclastic protolith or formed along a fault or through hydrothermal circulation. A few special names are used for rocks of unknown protolith but known modal composition, such as marble, eclogite, or amphibolite. Special names may also be applied more gener... | Metamorphic rock | Wikipedia | 504 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. The lower continental crust is mostly metamafic-rock and pelite which have reached the granulite facies. The middle continental crust is dominated by metamorphic rock that has reached the amphibolite facies. Within the... | Metamorphic rock | Wikipedia | 393 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Metamorphic rock of orogenic belts shows a variety of metamorphic facies. Where subduction is taking place, the basalt of the subducting slab is metamorphosed to high-pressure metamorphic facies. It initially undergoes low-grade metamorphism to metabasalt of the zeolite and prehnite-pumpellyite facies, but as the basa... | Metamorphic rock | Wikipedia | 436 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Metamorphic rock is also exposed in metamorphic core complexes, which form in region of crustal extension. They are characterized by low-angle faulting that exposes domes of middle or lower crust metamorphic rock. These were first recognized and studied in the Basin and Range Province of southwestern North America, but... | Metamorphic rock | Wikipedia | 457 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Contact metamorphism takes place when magma is injected into the surrounding solid rock (country rock). The changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms fro... | Metamorphic rock | Wikipedia | 494 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Quartzite is sufficiently hard and dense that it is difficult to quarry. However, some quartzite is used as dimension stone, often as slabs for flooring, walls, or stairsteps. About 6% of crushed stone, used mostly for road aggregate, is quartzite.
Marble is also prized for building construction and as a medium for sc... | Metamorphic rock | Wikipedia | 177 | 44424 | https://en.wikipedia.org/wiki/Metamorphic%20rock | Physical sciences | Petrology | null | vital_articles |
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than ... | Pluto | Wikipedia | 483 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
In 1906, Percival Lowell—a wealthy Bostonian who had founded Lowell Observatory in Flagstaff, Arizona, in 1894—started an extensive project in search of a possible ninth planet, which he termed "Planet X". By 1909, Lowell and William H. Pickering had suggested several possible celestial coordinates for such a planet. L... | Pluto | Wikipedia | 436 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Upon the announcement of the discovery, Lowell Observatory received over a thousand suggestions for names. Three names topped the list: Minerva, Pluto and Cronus. 'Minerva' was the Lowell staff's first choice but was rejected because it had already been used for an asteroid; Cronus was disfavored because it was promote... | Pluto | Wikipedia | 471 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
The name 'Pluto' was soon embraced by wider culture. In 1930, Walt Disney was apparently inspired by it when he introduced for Mickey Mouse a canine companion named Pluto, although Disney animator Ben Sharpsteen could not confirm why the name was given. In 1941, Glenn T. Seaborg named the newly created element plutoniu... | Pluto | Wikipedia | 449 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
In 1978, the discovery of Pluto's moon Charon allowed the measurement of Pluto's mass for the first time: roughly 0.2% that of Earth, and far too small to account for the discrepancies in the orbit of Uranus. Subsequent searches for an alternative Planet X, notably by Robert Sutton Harrington, failed. In 1992, Myles St... | Pluto | Wikipedia | 332 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Ceres, Pallas, Juno and Vesta lost their planet status among most astronomers after the discovery of many other asteroids in the 1840s. On the other hand, planetary geologists often regarded Ceres, and less often Pallas and Vesta, as being different from smaller asteroids because they were large enough to have undergon... | Pluto | Wikipedia | 509 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
There has been some resistance within the astronomical community toward the reclassification, and in particular planetary scientists often continue to reject it, considering Pluto, Charon, and Eris to be planets for the same reason they do so for Ceres. In effect, this amounts to accepting only the second clause of the... | Pluto | Wikipedia | 409 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Researchers on both sides of the debate gathered in August 2008, at the Johns Hopkins University Applied Physics Laboratory for a conference that included back-to-back talks on the IAU definition of a planet. Entitled "The Great Planet Debate", the conference published a post-conference press release indicating that sc... | Pluto | Wikipedia | 431 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Despite Pluto's orbit appearing to cross that of Neptune when viewed from north or south of the Solar System, the two objects' orbits do not intersect. When Pluto is closest to the Sun, and close to Neptune's orbit as viewed from such a position, it is also the farthest north of Neptune's path. Pluto's orbit passes abo... | Pluto | Wikipedia | 333 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
The 2:3 resonance between the two bodies is highly stable and has been preserved over millions of years. This prevents their orbits from changing relative to one another, so the two bodies can never pass near each other. Even if Pluto's orbit were not inclined, the two bodies could never collide. When Pluto's period is... | Pluto | Wikipedia | 479 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Second, the longitudes of ascending nodes of the two bodies—the points where they cross the invariant plane—are in near-resonance with the above libration. When the two longitudes are the same—that is, when one could draw a straight line through both nodes and the Sun—Pluto's perihelion lies exactly at 90°, and hence i... | Pluto | Wikipedia | 482 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
The plains on Pluto's surface are composed of more than 98 percent nitrogen ice, with traces of methane and carbon monoxide. Nitrogen and carbon monoxide are most abundant on the anti-Charon face of Pluto (around 180° longitude, where Tombaugh Regio's western lobe, Sputnik Planitia, is located), whereas methane is most... | Pluto | Wikipedia | 472 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Pluto's density is . Because the decay of radioactive elements would eventually heat the ices enough for the rock to separate from them, scientists expect that Pluto's internal structure is differentiated, with the rocky material having settled into a dense core surrounded by a mantle of water ice. The pre–New Horizons... | Pluto | Wikipedia | 506 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
The discovery of Pluto's satellite Charon in 1978 enabled a determination of the mass of the Pluto–Charon system by application of Newton's formulation of Kepler's third law. Observations of Pluto in occultation with Charon allowed scientists to establish Pluto's diameter more accurately, whereas the invention of adapt... | Pluto | Wikipedia | 220 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Pluto has a tenuous atmosphere consisting of nitrogen (N2), methane (CH4), and carbon monoxide (CO), which are in equilibrium with their ices on Pluto's surface. According to the measurements by New Horizons, the surface pressure is about 1 Pa (10 μbar), roughly one million to 100,000 times less than Earth's atmospheri... | Pluto | Wikipedia | 476 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Pluto has five known natural satellites. The largest and closest to Pluto is Charon. First identified in 1978 by astronomer James Christy, Charon is the only moon of Pluto that may be in hydrostatic equilibrium. Charon's mass is sufficient to cause the barycenter of the Pluto–Charon system to be outside Pluto. Beyond C... | Pluto | Wikipedia | 480 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Pluto's moons are hypothesized to have been formed by a collision between Pluto and a similar-sized body, early in the history of the Solar System. The collision released material that consolidated into the moons around Pluto.
Quasi-satellite
In 2012, it was calculated that 15810 Arawn could be a quasi-satellite of ... | Pluto | Wikipedia | 484 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Though Pluto is the largest Kuiper belt object discovered, Neptune's moon Triton, which is larger than Pluto, is similar to it both geologically and atmospherically, and is thought to be a captured Kuiper belt object. Eris (see above) is about the same size as Pluto (though more massive) but is not strictly considered ... | Pluto | Wikipedia | 445 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Pluto's distance from Earth makes its in-depth study and exploration difficult. Pluto's visual apparent magnitude averages 15.1, brightening to 13.65 at perihelion. To see it, a telescope is required; around 30 cm (12 in) aperture being desirable. It looks star-like and without a visible disk even in large telescopes, ... | Pluto | Wikipedia | 298 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
The New Horizons spacecraft, which flew by Pluto in July 2015, is the first and so far only attempt to explore Pluto directly. Launched in 2006, it captured its first (distant) images of Pluto in late September 2006 during a test of the Long Range Reconnaissance Imager. The images, taken from a distance of approximatel... | Pluto | Wikipedia | 277 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Since the New Horizons flyby, scientists have advocated for an orbiter mission that would return to Pluto to fulfill new science objectives. They include mapping the surface at per pixel, observations of Pluto's smaller satellites, observations of how Pluto changes as it rotates on its axis, investigations of a possib... | Pluto | Wikipedia | 455 | 44469 | https://en.wikipedia.org/wiki/Pluto | Physical sciences | Solar System | null | vital_articles |
Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about nine times that of Earth. It has an eighth the average density of Earth, but is over 95 times more massive. Even though Saturn is almost as big as Jupiter, Saturn has les... | Saturn | Wikipedia | 478 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Physical characteristics
Saturn is a gas giant, composed predominantly of hydrogen and helium. It lacks a definite surface, though it is likely to have a solid core. The planet's rotation makes it an oblate spheroid—a ball flattened at the poles and bulging at the equator. Its equatorial radius is more than 10% larger... | Saturn | Wikipedia | 425 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
This core is similar in composition to Earth, but is more dense. The examination of Saturn's gravitational moment, in combination with physical models of the interior, has allowed constraints to be placed on the mass of Saturn's core. In 2004, scientists estimated that the core must be 9–22 times the mass of Earth, whi... | Saturn | Wikipedia | 435 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Trace amounts of ammonia, acetylene, ethane, propane, phosphine, and methane have been detected in Saturn's atmosphere. The upper clouds are composed of ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide () or water. Ultraviolet radiation from the Sun causes methane photoly... | Saturn | Wikipedia | 386 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters, and in 1994 another smaller storm was observed. The 1990 storm was a... | Saturn | Wikipedia | 484 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor any hexagonal standing wave. NASA reported in November 2006 that Cassini had observed a "hurricane-like" storm locked to the south pole that had a clearly defined eyewall. Eyewall clouds had not previously been ... | Saturn | Wikipedia | 506 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Astronomers use three different systems for specifying the rotation rate of Saturn. System I has a period of (844.3°/d) and encompasses the Equatorial Zone, the South Equatorial Belt, and the North Equatorial Belt. The polar regions are considered to have rotation rates similar to System I. All other Saturnian latitud... | Saturn | Wikipedia | 416 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Saturn has 146 known moons, 63 of which have formal names. It is estimated that there are another outer irregular moons larger than in diameter. In addition, there is evidence of dozens to hundreds of moonlets with diameters of 40–500 meters in Saturn's rings, which are not considered to be true moons. Titan, the lar... | Saturn | Wikipedia | 505 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
There is a debate on the age of the rings. One side supports that they are ancient, and were created simultaneously with Saturn from the original nebular material (around 4.6 billion years ago), or shortly after the LHB (around 4.1 to 3.8 billion years ago). The other side supports that they are much younger, created a... | Saturn | Wikipedia | 465 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
The Greek scientist Ptolemy based his calculations of Saturn's orbit on observations he made while it was in opposition. In Hindu astrology, there are nine astrological objects, known as Navagrahas. Saturn is known as "Shani" and judges everyone based on the good and bad deeds performed in life. Ancient Chinese and Jap... | Saturn | Wikipedia | 495 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Pioneer 11 made the first flyby of Saturn in September 1979, when it passed within of the planet's cloud tops. Images were taken of the planet and a few of its moons, although their resolution was too low to discern surface detail. The spacecraft also studied Saturn's rings, revealing the thin F-ring and the fact that... | Saturn | Wikipedia | 499 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
In 2006, NASA reported that Cassini had found evidence of liquid water reservoirs no more than tens of meters below the surface that erupt in geysers on Saturn's moon Enceladus. These jets of icy particles are emitted into orbit around Saturn from vents in the moon's south polar region. Over 100 geysers have been ident... | Saturn | Wikipedia | 424 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Saturn is the most distant of the five planets easily visible to the naked eye from Earth, the other four being Mercury, Venus, Mars, and Jupiter. (Uranus, and occasionally 4 Vesta, are visible to the naked eye in dark skies.) Saturn appears to the naked eye in the night sky as a bright, yellowish point of light. The m... | Saturn | Wikipedia | 458 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
From time to time, Saturn is occulted by the Moon (that is, the Moon covers up Saturn in the sky). As with all the planets in the Solar System, occultations of Saturn occur in "seasons". Saturnian occultations will take place monthly for about a 12-month period, followed by about a five-year period in which no such act... | Saturn | Wikipedia | 248 | 44474 | https://en.wikipedia.org/wiki/Saturn | Physical sciences | Astronomy | null | vital_articles |
Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a supercritical phase of matter, which astronomy calls "ice" or volatiles. The planet's atmosphere has a complex layered cloud structure and has the lowest minimum temperature... | Uranus | Wikipedia | 417 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Uranus is visible to the naked eye, but it is very dim and was not classified as a planet until 1781, when it was first observed by William Herschel. About seven decades after its discovery, consensus was reached that the planet be named after the Greek god Uranus (Ouranos), one of the Greek primordial deities. As of 2... | Uranus | Wikipedia | 494 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Herschel recorded in his journal: "In the quartile near ζ Tauri ... either [a] Nebulous star or perhaps a comet." On 17 March he noted: "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place." When he presented his discovery to the Royal Society, he continued to assert that ... | Uranus | Wikipedia | 415 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Name
The name Uranus references the ancient Greek deity of the sky Uranus (), known as Caelus in Roman mythology, the father of Cronus (Saturn), grandfather of Zeus (Jupiter) and the great-grandfather of Ares (Mars), which was rendered as in Latin (). It is the only one of the eight planets whose English name derives... | Uranus | Wikipedia | 434 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
In a March 1782 treatise, Johann Elert Bode proposed Uranus, the Latinised version of the Greek god of the sky, Ouranos. Bode argued that the name should follow the mythology so as not to stand out as different from the other planets, and that Uranus was an appropriate name as the father of the first generation of the ... | Uranus | Wikipedia | 442 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Uranus is called by a variety of names in other languages. Uranus's name is literally translated as the "Heavenly King star" in Chinese (), Japanese (天王星), Korean (천왕성), and Vietnamese (sao Thiên Vương). In Thai, its official name is (), as in English. Its other name in Thai is (, Star of Mṛtyu), after the Sanskrit w... | Uranus | Wikipedia | 509 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The orbital elements of Uranus were first calculated in 1783 by Pierre-Simon Laplace. With time, discrepancies began to appear between predicted and observed orbits, and in 1841, John Couch Adams first proposed that the differences might be due to the gravitational tug of an unseen planet. In 1845, Urbain Le Verrier be... | Uranus | Wikipedia | 487 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
One result of this axis orientation is that, averaged over the Uranian year, the near-polar regions of Uranus receive a greater energy input from the Sun than its equatorial regions. Nevertheless, Uranus is hotter at its equator than at its poles. The underlying mechanism that causes this is unknown. The reason for Ura... | Uranus | Wikipedia | 367 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Uranus's mass is roughly 14.5 times that of Earth, making it the least massive of the giant planets. Its diameter is slightly larger than Neptune's at roughly four times that of Earth. A resulting density of 1.27 g/cm3 makes Uranus the second least dense planet, after Saturn. This value indicates that it is made primar... | Uranus | Wikipedia | 491 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The bulk compositions of Uranus and Neptune are different from those of Jupiter and Saturn, with ice dominating over gases, hence justifying their separate classification as ice giants. There may be a layer of ionic water where the water molecules break down into a soup of hydrogen and oxygen ions, and deeper down supe... | Uranus | Wikipedia | 429 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
One of the hypotheses for this discrepancy suggests the Earth-sized impactor theorised to be behind Uranus's axial tilt left the planet with a depleted core temperature, as the impact caused Uranus to expel most of its primordial heat. Another hypothesis is that some form of barrier exists in Uranus's upper layers that... | Uranus | Wikipedia | 388 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The composition of Uranus's atmosphere is different from its bulk, consisting mainly of molecular hydrogen and helium. The helium molar fraction, i.e. the number of helium atoms per molecule of gas, is in the upper troposphere, which corresponds to a mass fraction . This value is close to the protosolar helium mass fr... | Uranus | Wikipedia | 461 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The troposphere is thought to have a highly complex cloud structure; water clouds are hypothesised to lie in the pressure range of , ammonium hydrosulfide clouds in the range of , ammonia or hydrogen sulfide clouds at between and finally directly detected thin methane clouds at . The troposphere is a dynamic part of t... | Uranus | Wikipedia | 482 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
This extended corona is a unique feature of Uranus. Its effects include a drag on small particles orbiting Uranus, causing a general depletion of dust in the Uranian rings. The Uranian thermosphere, together with the upper part of the stratosphere, corresponds to the ionosphere of Uranus. Observations show that the ion... | Uranus | Wikipedia | 389 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Voyager 2 arrived during the height of Uranus's southern summer and could not observe the northern hemisphere. At the beginning of the 21st century, when the northern polar region came into view, the Hubble Space Telescope (HST) and Keck telescope initially observed neither a collar nor a polar cap in the northern hemi... | Uranus | Wikipedia | 369 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The tracking of numerous cloud features allowed determination of zonal winds blowing in the upper troposphere of Uranus. At the equator winds are retrograde, which means that they blow in the reverse direction to the planetary rotation. Their speeds are from . Wind speeds increase with the distance from the equator, re... | Uranus | Wikipedia | 449 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
For a short period from March to May 2004, large clouds appeared in the Uranian atmosphere, giving it a Neptune-like appearance. Observations included record-breaking wind speeds of and a persistent thunderstorm referred to as "Fourth of July fireworks". On 23 August 2006, researchers at the Space Science Institute (B... | Uranus | Wikipedia | 418 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
In the 1990s, as Uranus moved away from its solstice, Hubble and ground-based telescopes revealed that the south polar cap darkened noticeably (except the southern collar, which remained bright), whereas the northern hemisphere demonstrated increasing activity, such as cloud formations and stronger winds, bolstering ex... | Uranus | Wikipedia | 504 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Studies of Voyager 2 data in 2017 suggest that this asymmetry causes Uranus's magnetosphere to connect with the solar wind once a Uranian day, opening the planet to the Sun's particles. In comparison, the magnetic field of Earth is roughly as strong at either pole, and its "magnetic equator" is roughly parallel with it... | Uranus | Wikipedia | 332 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Despite its curious alignment, in other respects the Uranian magnetosphere is like those of other planets: it has a bow shock at about 23 Uranian radii ahead of it, a magnetopause at 18 Uranian radii, a fully developed magnetotail, and radiation belts. Overall, the structure of Uranus's magnetosphere is different from ... | Uranus | Wikipedia | 413 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Uranus has 28 known natural satellites. The names of these satellites are chosen from characters in the works of Shakespeare and Alexander Pope. The five main satellites are Miranda, Ariel, Umbriel, Titania, and Oberon. The Uranian satellite system is the least massive among those of the giant planets; the combined mas... | Uranus | Wikipedia | 414 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
The Uranian rings are composed of extremely dark particles, which vary in size from micrometres to a fraction of a metre. Thirteen distinct rings are presently known, the brightest being the ε ring. All except the two rings of Uranus are extremely narrow—they are usually a few kilometres wide. The rings are probably qu... | Uranus | Wikipedia | 374 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
In December 2005, the Hubble Space Telescope detected a pair of previously unknown rings. The largest is located twice as far from Uranus as the previously known rings. These new rings are so far from Uranus that they are called the "outer" ring system. Hubble also spotted two small satellites, one of which, Mab, share... | Uranus | Wikipedia | 351 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
No other spacecraft has flown by Uranus since then, though there have been many proposed missions to revisit the Uranus system. The possibility of sending the Cassini spacecraft from Saturn to Uranus was evaluated during a mission extension planning phase in 2009, but was ultimately rejected in favour of destroying it ... | Uranus | Wikipedia | 280 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
In modern astrology, the planet Uranus (symbol ) is the ruling planet of Aquarius; prior to the discovery of Uranus, the ruling planet of Aquarius was Saturn. Because Uranus is cyan and Uranus is associated with electricity, the colour electric blue, which is close to cyan, is associated with the sign Aquarius.
The ch... | Uranus | Wikipedia | 233 | 44475 | https://en.wikipedia.org/wiki/Uranus | Physical sciences | Astronomy | null | vital_articles |
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sand... | Tuff | Wikipedia | 406 | 44481 | https://en.wikipedia.org/wiki/Tuff | Physical sciences | Petrology | null | vital_articles |
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