"Planetary mnemonic A planetary mnemonic refers to a phrase used to remember the planets and dwarf planets of the Solar System, with the order of words corresponding to increasing sidereal periods of the bodies. One simple visual mnemonic is to hold out both hands side-by-side with fingers spread and thumbs in the same direction, with the fingers of one hand representing the terrestrial planets, and the other hand the gas giants. The first thumb represents the Sun and asteroid belt, including Ceres, and the second thumb represents the asteroid belt and trans-Neptunian objects, including Pluto. An English-language mnemonic which was"
"object that is neither a true planet nor a natural satellite; it is in direct orbit of a star, and is massive enough for its gravity to compress it into a hydrostatically equilibrious shape (usually a spheroid), but has not cleared the neighborhood of other material around its orbit. As of July 2008 the IAU has recognized five dwarf planets: Ceres in the asteroid belt, and Pluto, Haumea, Makemake, and Eris in the outer Solar System. Several computer simulations of stellar and planetary system formation have suggested that some objects of planetary mass would be ejected into interstellar space. Some"
"finally precipitated by the discovery of an even more massive object, Eris. The exclusion of dwarf planets from the roster of planets by the IAU has been both praised and criticized; it was said to be the ""right decision"" by astronomer Mike Brown, who discovered Eris and other new dwarf planets, but has been rejected by Alan Stern, who had coined the term ""dwarf planet"" in April 1991. As of July 2008 the International Astronomical Union (IAU) recognizes five dwarf planets: in the asteroid belt, and Pluto, , , and in the outer Solar System. Brown criticizes this official recognition:"
"the 26th General Assembly, is: The IAU further resolves: The IAU also resolved that """"planets"" and ""dwarf planets"" are two distinct classes of objects"", meaning that dwarf planets, despite their name, would not be considered planets. Alan Stern, the lead scientist on NASA's robotic mission to Pluto, contended that Earth, Mars, Jupiter, and Neptune have not fully cleared their orbital zones, just like Pluto. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path. Stern has asserted: ""If Neptune had cleared its zone, Pluto wouldn't be there."" Some astronomers counter this opinion"
"orbit as defined by the Titius–Bode law. Between 1845 and 1851, eleven additional asteroids were discovered and Jupiter had become the twentieth planet. At this point, astronomers began to classify asteroids as minor planets. Following the reclassification of the asteroids in their own group, Jupiter became the fifth planet once again. With the redefinition of the term ""planet"" in 2006, Ceres is now considered a dwarf planet. The disruption theory suggests that a planet which was positioned between Mars and Jupiter was destroyed, resulting in the asteroid belt between these planets. Scientists in the 20th century dubbed this hypothetical planet"
"other orbiting matter. ""Dawn"" is the first mission to study a dwarf planet, arriving at Ceres a few months before the arrival of the ""New Horizons"" probe at Pluto in July 2015. Ceres comprises a third of the total mass of the asteroid belt. Its spectral characteristics suggest a composition similar to that of a water-rich carbonaceous chondrite. Vesta, a smaller, water-poor achondritic asteroid comprising a tenth of the mass of the asteroid belt, has experienced significant heating and differentiation. It shows signs of a metallic core, a Mars-like density and lunar-like basaltic flows. Available evidence indicates that both bodies"
"Identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to these two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds, freely travel between regions. Six of the planets, at least four of the dwarf planets, and many of the smaller bodies are orbited by natural satellites, usually termed ""moons"" after the Moon. Each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region in the interstellar medium"
"Pluto Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union (IAU) to"
"they may have arisen from the same collisional event. All members have a relatively high orbital inclination. 31 Euphrosyne Euphrosyne (minor planet designation: 31 Euphrosyne) is the 12th-largest and the 5th-most-massive asteroid in the asteroid belt, discovered by James Ferguson on September 1, 1854. It was the first asteroid found from North America. It is named after Euphrosyne, one of the Charites in Greek mythology. It is a fairly dark body near the belt's outer edge. Consequently, Euphrosyne is never visible with binoculars, having a maximum magnitude at the best possible opposition of around +10.2, as in November 2011, which"
"era. The fifth terrestrial planet began on a low-eccentricity orbit between Mars and the asteroid belt with a semi-major axis between 1.8 and 1.9 AU. While long-lived, this orbit was unstable on a time-scale of 600 Myr. Eventually perturbations from the other inner planets drove Planet V onto a high-eccentricity orbit which crossed into the inner asteroid belt. Asteroids were scattered onto Mars-crossing and resonant orbits by close encounters with Planet V. Many of these asteroids then evolved onto Earth-crossing orbits temporarily enhancing the lunar impact rate. This process continued until Planet V was lost most likely by impacting the"
"program describes a fusion-enabled Pluto orbiter and lander based on the Princeton field-reversed configuration reactor. Pluto Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is"
"dwarf planets and the other eight planets based on their inability to ""clear the neighborhood around their orbits"", although his proposal suggested the terms ""unterplanet"" and ""überplanet"" and used the word ""dwarf"" to mean something else. Harold F. Levison Harold F. (Hal) Levison is a planetary scientist specializing in planetary dynamics. He currently works at the Southwest Research Institute, Boulder, CO, and studies planetary orbits and their evolution through solar system history. Levison is the Principal Investigator of the Lucy mission to tour multiple Jupiter trojans which was selected as the thirteenth mission in NASA's Discovery Program in January 2017."
"""A reasonable person might think that this means that there are five known objects in the solar system which fit the IAU definition of dwarf planet, but this reasonable person would be nowhere close to correct."" Another hundred or so known objects in the Solar System are suspected to be dwarf planets. Estimates are that up to 200 dwarf planets will be identified when the entire region known as the Kuiper belt is explored, and that the number may exceed 10,000 when objects scattered outside the Kuiper belt are considered. Individual astronomers recognize several of these, and Brown maintains a"
"Planet V Planet V is a hypothetical fifth terrestrial planet posited by NASA scientists John Chambers and Jack J. Lissauer to have once existed between Mars and the asteroid belt. In their hypothesis the Late Heavy Bombardment of the Hadean era began after perturbations from the other terrestrial planets caused Planet V's orbit to cross into the asteroid belt. Chambers and Lissauer presented the results of initial tests of this hypothesis during the 33rd Lunar and Planetary Science Conference, held from March 11 through 15, 2002. In the Planet V hypothesis five terrestrial planets were produced during the planetary formation"
"ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region. The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though he did not predict its existence. In 1992, Albion was discovered, the first Kuiper belt object (KBO) since Pluto and Charon. Since its discovery, the number of known KBOs has increased to over a thousand, and more than 100,000 KBOs over in diameter are thought to exist. The Kuiper belt was initially"
"observed Astraea in March 2012. 5 Astraea Astraea (minor planet designation: 5 Astraea) is a large asteroid from the asteroid belt. Its surface is highly reflective (bright) and its composition is probably a mixture of nickel–iron with silicates of magnesium and iron. It is a S-type object in the Tholen classification system. Astraea was the fifth asteroid discovered, on 8 December 1845, by Karl Ludwig Hencke and named for ""Astræa"", a goddess of justice named after the stars. It was his first of two asteroid discoveries. The second was 6 Hebe. A German amateur astronomer and post office headmaster, Hencke"
"before Charon was discovered. Pluto is more than twice the diameter and a dozen times the mass of the dwarf planet Ceres, the largest object in the asteroid belt. It is less massive than the dwarf planet Eris, a trans-Neptunian object discovered in 2005, though Pluto has a larger diameter of 2376.6 km compared to Eris's approximate diameter of 2326 km. Determinations of Pluto's size had been complicated by its atmosphere, and hydrocarbon haze. In March 2014, Lellouch, de Bergh et al. published findings regarding methane mixing ratios in Pluto's atmosphere consistent with a Plutonian diameter greater than 2360 km,"
"lie within a nearly flat disc called the ecliptic. The Solar System also contains smaller objects. The asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, and beyond them a newly discovered population of sednoids. Within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets."
"by an attempt by the IAU division III plenary session to reinstate Pluto as a planet in a second resolution. Indeed, the draft of Resolution 5A had called these median bodies ""planetoids,"" but the plenary session voted unanimously to change the name to ""dwarf planet."" The second resolution, 5B, defined ""dwarf planets"" as a subtype of ""planet"", as Stern had originally intended, distinguished from the other eight that were to be called ""classical planets"". Under this arrangement, the twelve planets of the rejected proposal were to be preserved in a distinction between eight ""classical planets"" and four ""dwarf planets"". Resolution"
"5 Astraea Astraea (minor planet designation: 5 Astraea) is a large asteroid from the asteroid belt. Its surface is highly reflective (bright) and its composition is probably a mixture of nickel–iron with silicates of magnesium and iron. It is a S-type object in the Tholen classification system. Astraea was the fifth asteroid discovered, on 8 December 1845, by Karl Ludwig Hencke and named for ""Astræa"", a goddess of justice named after the stars. It was his first of two asteroid discoveries. The second was 6 Hebe. A German amateur astronomer and post office headmaster, Hencke was looking for 4 Vesta"
"of a probe and orbiter to Venus. Pioneer Terra Pioneer Terra is a region on the dwarf planet Pluto, north of Tombaugh Regio and east of Voyager Terra. It was discovered by the ""New Horizons"" spacecraft on 14 July 2015. It is named for the ""Pioneer"" program, which included ""Pioneer 10"" and ""Pioneer 11"", the first spacecraft to cross the asteroid belt and explore Jupiter and Saturn, as well as the first to explore the outer solar system; ""Pioneer 6, 7, 8, and 9"", which formed an ""interplanetary weather network""; ""Pioneer 1"" through ""5"", which explored the Moon in various"
"55 Cancri consists of a yellow dwarf and a smaller red dwarf, with five planets orbiting the primary star; one low-mass planet that may be either a hot, water-rich world or a carbon planet and four gas giants. 55 Cancri A, classified as a rare ""super metal-rich"" star, is one of the top 100 target stars for NASA's Terrestrial Planet Finder mission, ranked 63rd on the list. The red dwarf 55 Cancri B, a suspected binary, appears to be gravitationally bound to the primary star, as the two share common proper motion. YBP 1194 is a sunlike star in the"
"Jupiter. All brown dwarfs are either L dwarfs, T dwarfs or Y dwarfs, in order of decreasing temperature. An increasing number after the letter in the spectral type also means decreasing temperature, a Y2 dwarf is cooler than a Y1 dwarf is cooler than a Y0 dwarf. Planets can also be L dwarfs, T dwarfs or Y dwarfs. WISE 0535−7500 WISE J053516.80−750024.9 (designation abbreviated to WISE 0535−7500) is either a sub-brown dwarf or a free planet. It has spectral class ≥Y1 and is located in constellation Mensa. It is estimated to be 47 light-years from Earth. In 2017, more accurate"
"Only in 1949 did the well-known Soviet astronomer Sergej Vladirimovich Orlov give it the name Phaeton... This name has become established."" Theories regarding the formation of the asteroid belt from the destruction of a hypothetical fifth planet are today collectively referred to as the ""disruption theory"". This theory states that there was once a major planetary member of our solar system circulating in the present gap between Mars and Jupiter, which was variously destroyed when: Today, the Phaeton hypothesis has been superseded by the accretion model. Most astronomers today believe that the asteroids in the main belt are remnants of"
"31 Euphrosyne Euphrosyne (minor planet designation: 31 Euphrosyne) is the 12th-largest and the 5th-most-massive asteroid in the asteroid belt, discovered by James Ferguson on September 1, 1854. It was the first asteroid found from North America. It is named after Euphrosyne, one of the Charites in Greek mythology. It is a fairly dark body near the belt's outer edge. Consequently, Euphrosyne is never visible with binoculars, having a maximum magnitude at the best possible opposition of around +10.2, as in November 2011, which is actually fainter than any of the thirty asteroids previously discovered. It is a very little-studied body"
"term ""planet"" was redefined to exclude the new category of dwarf planets (just as some planets had earlier been recategorised as asteroids). In 2006 Pluto, Eris, Haumea, Makemake, and (in the inner Solar System) the asteroid Ceres were reclassified as dwarf planets. Eleventh planet Eleventh planet (of the Solar System) may refer to Vesta, the eleventh object to be named a planet, later to be reclassified as an asteroid; Uranus, the eleventh planet from the Sun upon Vesta's discovery, though this was quickly superseded by new discoveries; or Haumea, which would be the eleventh planet if the classification advocated by"
"to less than 0.01% of the Earth's mass. However, this does not exclude the presence of an asteroid belt or a Kuiper belt equivalent. The secondary, 55 Cancri B, is a red dwarf star much less massive and luminous than the Sun. There are indications that component B may itself be a double star, though this is uncertain. The 55 Cancri system was the first known to have four, and later five planets, and may possibly have more. The innermost planet, e, transits 55 Cancri A as viewed from Earth. The next planet, b, is non-transiting but there is tentative"
"in the main belt are family members. There are about 20 to 30 reliably recognized families, with several tens of less certain groupings. Most asteroid families are found in the main asteroid belt, although several family-like groups such as the Pallas family, Hungaria family, and the Phocaea family lie at smaller semi-major axis or larger inclination than the main belt. One family has been identified associated with the dwarf planet . Some studies have tried to find evidence of collisional families among the trojan asteroids, but at present the evidence is inconclusive. The families are thought to form as a"
"red dwarf star (though only lower limits are known for those planets detected by the radial velocity method). OGLE-2005-BLG-071Lb OGLE-2005-BLG-071Lb is a planet discovered by the Optical Gravitational Lensing Experiment (OGLE) and others in 2005, using gravitational microlensing. According to the best fit model, it has about 3.5 times the mass of Jupiter and a projected separation of 3.6 astronomical units from the star. This would result in an effective temperature around 50 K, similar to that of Neptune. However, an alternative model which gives a slightly lower mass of 3.3 times that of Jupiter and a projected separation of"
"July 2015, Astronomy & Astrophysics said they found a planetary system with three super-Earths orbiting a bright, dwarf star. The four-planet system, dubbed HD 219134, had been found 21 light years from Earth in the M-shaped northern hemisphere of constellation Cassiopeia, but it is not in the habitable zone of its star. The planet with the shortest orbit is HD 219134 b, and is Earth's closest known rocky, and transiting, exoplanet. In February 2016, it was announced that NASA Hubble Space Telescope had detected hydrogen and helium (and suggestions of hydrogen cyanide), but no water vapor, in the atmosphere of"
"Pioneer Terra Pioneer Terra is a region on the dwarf planet Pluto, north of Tombaugh Regio and east of Voyager Terra. It was discovered by the ""New Horizons"" spacecraft on 14 July 2015. It is named for the ""Pioneer"" program, which included ""Pioneer 10"" and ""Pioneer 11"", the first spacecraft to cross the asteroid belt and explore Jupiter and Saturn, as well as the first to explore the outer solar system; ""Pioneer 6, 7, 8, and 9"", which formed an ""interplanetary weather network""; ""Pioneer 1"" through ""5"", which explored the Moon in various ways; and the Pioneer Venus project, consisting"
"Geneva in Switzerland and Grenoble University in France. Detected in August 2005 and using extensive data from the ESO/HARPS spectrometer it was the fifth planet to be discovered around a red dwarf. Further observations by the same group resulted in the detection of two more planets, Gliese 581c and Gliese 581d. The orbital period of Gliese 581d was originally thought to be 83 days but was later revised to a lower value of 67 days. The revised orbital distance would place it at the outer limits of the habitable zone, the distance at which it is believed possible for liquid"
"into the Sun. Unlike the Disruption Theory's fifth planet, ""Planet V"" is not credited with creating the asteroid belt. The concept of a fifth planet which had been destroyed to make the asteroid belt, as in the Disruption Theory, has been a popular one in fiction. Fifth planet (hypothetical) In the history of astronomy, a handful of Solar System bodies have been counted as the fifth planet from the Sun. Under the present definition of a planet, Jupiter is counted as the fifth. There are three main ideas regarding hypothetical planets between Mars and Jupiter. During the early 19th century,"