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Subsatellite Point
A subsatellite, also known as a submoon or informally a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. It is inferred from the empirical study of natural satellites in the Solar System that subsatellites may be rare, albeit possible, elements of planetary systems. In the Solar System, the giant planets have large collections of natural satellites. The majority of detected exoplanets are giant planets; at least one, Kepler-1625b, may have a very large exomoon, named Kepler-1625b I, which could theoretically host a subsatellite. Nonetheless, aside from human-launched satellites in temporary lunar orbit, no subsatellite is known in the Solar System or beyond. In most cases, the tidal effects of the planet would make such a system unstable on an astronomical timescale. Terminology Terms used in scientific literature for subsatellites include "submoons" and "moon-moons". Colloquial terms that have been suggested include moonitos, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exomoon Kepler-1625b-I Orbiting Its Planet (artist’s Impression)
Artist's impression of candidate exomoon Kepler-1625b I orbiting its planet. An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body. Exomoons are difficult to detect and confirm using current techniques, and to date there have been no confirmed exomoon detections. However, observations from missions such as Kepler have observed a number of candidates. Two potential exomoons that may orbit rogue planets have also been detected by microlensing. In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. Some exomoons may be potential habitats for extraterrestrial life. Definition and designation Although traditional usage implies moons orbit a planet, the discovery of brown dwarfs with planet-sized satellites blurs the distinction between planets and moons, due to the low mass of brown dwarfs. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Binary (small Solar System Body)
A contact binary is a small Solar System body, such as a minor planet or comet, that is composed of two bodies that have gravitated toward each other until they touch, resulting in a bilobated, peanut-like overall shape. Contact binaries are distinct from true binary systems such as binary asteroids where both components are separated. The term is also used for stellar contact binaries. An example of a contact binary is the Kuiper belt object 486958 Arrokoth, which was imaged by the ''New Horizons'' spacecraft during its flyby in January 2019. History The existence of contact binary asteroids was first speculated by planetary scientist Allan F. Cook in 1971, who sought for potential explanations for the extremely elongated shape of the Jupiter trojan asteroid 624 Hektor, whose longest axis measures roughly across and is twice as long as its shorter axes according to light curve measurements. Astronomers William K. Hartmann and Dale P. Cruikshank performed further invest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiviuq (moon)
Kiviuq is a prograde irregular satellite of Saturn. It was discovered by J. J. Kavelaars et al. in 2000, and given the temporary designation S/2000 S 5. It was named after Kiviuq, a hero of Inuit mythology. Kiviuq is about 17 km in diameter, and orbits Saturn at an average distance of 11.3 million kilometers in 449 days. It is a member of the Inuit group of irregular satellites. It is light red, and the Kiviupian (Kiviuqan) infrared spectrum is very similar to the Inuit-group satellites Siarnaq and Paaliaq, supporting the thesis of a possible common origin of the Inuit group in the break-up of a larger body. Kiviuq is believed to be in Kozai resonance, cyclically reducing its orbital inclination while increasing the eccentricity and vice versa. Its current orbital elements overlap strongly with Phoebe's orbit, and the moons will likely eventually collide with each other. The light curve amplitude of Kiviuq is large, varying in brightness by over 2 magnitudes. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Heavy Bombardment
The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized astronomical event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypothesis, during this interval, a disproportionately large number of asteroids and comets collided into the terrestrial planets and their natural satellites in the inner Solar System, including Mercury, Venus, Earth (and the Moon) and Mars. These came from both post-accretion and planetary instability-driven populations of impactors. Although it gained widespread credence, definitive evidence remains elusive. Evidence for the LHB derives from moon rock samples of Lunar craters brought back by the Apollo program astronauts. Isotopic dating showed that the rocks were last molten during impact events in a rather narrow interval of time, suggesting that a large proportion of craters were formed during this period. Several hypo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oberon (moon)
Oberon , also designated , is the outermost and second-largest major moon of the planet Uranus. It is the second-most massive of the Uranian moons, and the tenth-largest moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after the mythical king of the fairies who appears as a character in Shakespeare's ''A Midsummer Night's Dream''. Its orbit lies partially outside Uranus's magnetosphere. Oberon likely formed from the accretion disk that surrounded Uranus just after the planet's formation. The moon consists of approximately equal amounts of ice and rock, and is probably differentiated into a rocky core and an icy mantle. A layer of liquid water may be present at the boundary between the mantle and the core. The surface of Oberon, which is dark and slightly red in color, appears to have been primarily shaped by asteroid and comet impacts. It is covered by numerous impact craters reaching 210 km in diameter. Oberon possesses a system of ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roche Limit
In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, held together only by its own force of gravity, will disintegrate because the first body's tidal forces exceed the second body's self-gravitation. Inside the Roche limit, orbiting material disperses and forms rings, whereas outside the limit, material tends to coalesce. The Roche radius depends on the radius of the second body and on the ratio of the bodies' densities. The term is named after Édouard Roche (, ), the French astronomer who first calculated this theoretical limit in 1848. Explanation The Roche limit typically applies to a satellite's disintegrating due to tidal forces induced by its ''primary'', the body around which it orbits. Parts of the satellite that are closer to the primary are attracted more strongly by gravity from the primary than parts that are farther away; this disparity effectively pulls the near an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tidal Locking
Tidal locking between a pair of co-orbiting astronomical body, astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where a tidally locked body possesses synchronous rotation, the object takes just as long to rotate around its own axis as it does to revolve around its partner. For example, the same side of the Moon always faces Earth, although there is some libration, variability because the Moon's orbit is not perfectly circular. Usually, only the natural satellite, satellite is tidally locked to the larger body. However, if both the difference in mass between the two bodies and the distance between them are relatively small, each may be tidally locked to the other; this is the case for Pluto and Charon (moon), Charon, and for Eris (dwarf planet), Eris and Dysnomia (moon), Dysnomia. Alternative names for the tidal locking process are gravitational locking, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washington University In St
Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on Washington, D.C. Washington may also refer to: Places England * Washington Old Hall, ancestral home of the family of George Washington * Washington, Tyne and Wear, a town in the City of Sunderland metropolitan borough * Washington, West Sussex, a village and civil parish Greenland * Cape Washington, Greenland * Washington Land Philippines *New Washington, Aklan, a municipality *Washington, a barangay in Catarman, Northern Samar *Washington, a barangay in Escalante, Negros Occidental *Washington, a barangay in San Jacinto, Masbate *Washington, a barangay in Surigao City United States * Fort Washington (disambiguati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equatorial Ridge On Iapetus
A 20 kilometer (12 mi) high mountain feature on Saturn’s moon Iapetus, commonly referred to as the “equatorial ridge,” is the third tallest mountain structure in the Solar System. It runs along most of Iapetus's equator, and was discovered by the '' Cassini'' probe in 2004. The ridge's origin is unknown. There are bright areas on the sides of the equatorial ridge near Iapetus' bright trailing hemisphere, which were already visible in ''Voyager 2'' images appearing like mountains and were nicknamed the "Voyager Mountains". Discovery Iapetus's equatorial ridge was discovered when the ''Cassini'' spacecraft imaged Iapetus on 31 December 2004. Peaks in the ridge rise more than 20 km above the surrounding plains, making them some of the tallest mountains in the Solar System. The ridge forms a complex system including isolated peaks, segments of more than 200 km and sections with three near parallel ridges. Origins Within the bright regions there is no ridge, but t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iapetus (moon)
Iapetus () is the outermost of Moons of Saturn, Saturn's large moons. With an estimated diameter of , it is the third-largest moon of Saturn and the List of natural satellites, eleventh-largest in the Solar System. Named after the Titans, Titan Iapetus, the moon was discovered in 1671 by Giovanni Domenico Cassini. A relatively low-density body made up mostly of ice, Iapetus is home to several distinctive and unusual features, such as a striking difference in coloration between its leading hemisphere, which is dark, and its trailing hemisphere, which is bright, as well as a massive Equatorial ridge on Iapetus, equatorial ridge running three-quarters of the way around the moon. History Discovery Iapetus was discovered by Giovanni Domenico Cassini, an Italian-born French astronomer, in October 1671. This is the first moon that Cassini discovered; the second moon of Saturn to be discovered after Christiaan Huygens spotted Titan (moon), Titan 16 years prior in 1655; and the sixth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shepherd Moon
A shepherd moon is a small natural satellite that clears a gap in planetary ring material or keeps particles within a ring contained. The name is a result of their limiting the "herd" of the ring particles as a shepherd. Due to their gravitational influence, shepherd moons deflect ring particles from their original orbits due to proximity or through orbital resonances. This can carve gaps in the ring system, such as the Encke Gap maintained by Saturn's moon Pan, or lead to the confining of narrow ringlets, such as Saturn's F ring. Discovery The existence of shepherd moons was theorized in early 1979. Observations of the rings of Uranus show that they are very thin and well defined, with sharp gaps between rings. To explain this, Goldreich and Tremaine suggested that two small satellites that were undetected at the time might be confining each ring. The first images of shepherd satellites were taken later that year by Voyager 1. Examples Jupiter Several of Jupiter's sm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
