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	Topics Minor planet Topic Home An asteroid group consists of a set of minor planets that have a relatively loose dynamical associations. Members of a group can be unrelated to each other, unlike in a asteroid familyFacts About Asteroid family An asteroid family is a group of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, an... , which can result from the break-up of a single asteroid. It is customary to name a group of asteroids after the first member of that group to be discovered (often the largest). Groups out to the orbit of Earth There are relatively few asteroids that orbit close to the Sun. Several of these groups are hypothetical at this point in time, with no members having yet been discovered; as such, the names they have been given are provisional. Vulcanoid asteroidVulcanoid asteroid Vulcanoids are hypothetical group of asteroids that may orbit in a dynamically stable zone between 0.08 and 0.21 astronomica... s are hypothetical asteroids with an aphelion less than 0.4 AU, ie, they orbit entirely within the orbit of MercuryFacts About Mercury (planet) Mercury is the nearest planet to the sun, orbiting at an average distance of about 58 million kilometers.... . A few searches for Vulcanoids have been conducted but there have been none discovered so far. ApoheleApohele asteroid Apohele asteroids are a subclass of Aten asteroids.... s are asteroids whose aphelion is less than 0.983 AU, meaning they orbit entirely within Earth's orbit. "Apohele" is Hawaiian for "orbit". Other proposed names for this group are Inner-Earth Objects or Interior Earth Objects (IEOs) and Anons (as in "Anonymous"). As of March 2008 there are only five known Apoheles with an arc of observations greater than 20 days: (163693) Atira, , , and ; while there are other four possible candidates, but with a too short arc of observations: , , and . Mercury-crosser asteroids having a perihelion smaller than Mercury's 0.3075 AU. Venus-crosser asteroidVenus-crosser asteroid A Venus-crosser asteroid is an asteroid whose orbit crosses that of Venus.... s having a perihelion smaller than VenusVenus Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days.... 's 0.7184 AU. This group includes the above Mercury-crossers (if their aphelion is greater than Venus's perihelion. All known Mercury crossers satisfy this condition). Earth-crosser asteroidEarth-crosser asteroid Overview An Earth-crosser asteroid is a Near-Earth asteroid whose orbit crosses that of Earth.... s having a perihelion smaller than EarthEarth Earth is the third planet in the solar system in terms of distance from the Sun, and the fifth largest.... 's 0.9833 AU. This group includes the above Mercury- and Venus-crossers, apart from the Apoheles. They are also divided into the Aten asteroidAten asteroid The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered.... s having a semi-major axisSemi-major axis In geometry, the term semi-major axis is used to describe the dimensions of ellipses and hyperbolae. ... less than 1 AU, named after 2062 Aten2062 Aten 2062 Aten is an asteroid that was discovered at the Palomar Mountain Observatory by Eleanor F.... . Apollo asteroidApollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be dis... s having a semi-major axisSemi-major axis Summary In geometry, the term semi-major axis is used to describe the dimensions of ellipses and hyperbolae. ... greater than 1 AU, named after 1862 Apollo1862 Apollo 1862 Apollo is a Q-type asteroid, discovered by Karl Reinmuth in 1932, but lost and not recovered until 1973.... . Arjuna asteroidArjuna asteroid The Arjuna asteroids are a class of near-Earth asteroids whose orbits are very Earth-like in character, having low inclinati... s are somewhat vaguely defined as having orbits similar to Earth's; i.e., with an average orbital radius of around 1 AU and with low eccentricity and inclination. Due to the vagueness of this definition some asteroids belonging to the ApoheleApohele asteroid Apohele asteroids are a subclass of Aten asteroids.... , AmorAmor asteroid The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor.... , ApolloApollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be dis... or AtenAten asteroid The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered.... groups can also be classified as Arjunas. The term was introduced by SpacewatchSpacewatch Spacewatch is a project at the University of Arizona that specializes in the study of minor planets, including various types... and does not refer to an existing asteroid; examples of Arjunas include 1991 VG. Earth TrojanEarth Trojan asteroid Earth Trojans are asteroids located in the Earth-Sun Lagrangian points L4 and L5.... s are asteroids located in the Earth-Sun Lagrangian pointLagrangian point The Lagrangian points ; also Lagrange point, L-point, or libration point), are the five positions in inter... s L₄ and L₅. Their location in the sky as observed from Earth's surface would be fixed at about 60 degrees east and west of the Sun, and as people tend to search for asteroids at much greater elongations few searches have been done in these locations. No Earth trojans are currently known. Near-Earth asteroidNear-Earth asteroid Near-Earth asteroids are asteroids whose orbits are close to Earth's orbit.... s is a catch-all group for asteroids whose orbit closely approaches that of Earth. It includes almost all of the above groups, as well as the Amor asteroidAmor asteroid The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor.... s. Groups out to the orbit of Mars The AmorAmor asteroid The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor.... asteroids, named after 1221 Amor1221 Amor Overview 1221 Amor is the namesake of the Amor asteroids, a group of near-Earth asteroids whose orbits range between those of Earth a... are Near-Earth asteroidNear-Earth asteroid Near-Earth asteroids are asteroids whose orbits are close to Earth's orbit.... s that are not Earth-crossersEarth-crosser asteroid An Earth-crosser asteroid is a Near-Earth asteroid whose orbit crosses that of Earth.... , having a perihelion just outside the Earth's orbit. Mars-crosser asteroidMars-crosser asteroid A Mars-crosser asteroid is an asteroid whose orbit crosses that of Mars.... s have orbits that cross that of Mars, but do not necessarily closely approach the Earth's. Mars TrojanMars Trojan asteroid Mars Trojans are a large group of objects that share the orbit of the planet Mars around the Sun.... s follow or lead Mars on its orbit, at either of the two Lagrangian pointLagrangian point The Lagrangian points ; also Lagrange point, L-point, or libration point), are the five positions in inter... s 60° ahead (L₄) or behind (L₅). As of March 2008, four are known. The largest appears to be 5261 Eureka5261 Eureka 5261 Eureka was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Trojan asteroid.... . Many of the Earth- Venus- and Mercury-crosser asteroids have aphelia greater than 1AU. The main asteroid belt The overwhelming majority of known asteroids have orbits lying between the orbits of MarsMars Overview Mars is the fourth planet from the Sun in our solar system and is named after Mars, the Roman god of war.... and JupiterJupiter Jupiter is the fifth planet from the Sun and the largest within the solar system.... , roughly between 2 to 4 AUAstronomical unit The astronomical unit is a unit of length.... . These could not form a planet due to the gravitational influence of Jupiter. Jupiter's gravitational influence, through orbital resonanceOrbital resonance In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influen... , clears Kirkwood gapKirkwood gap Kirkwood gaps are gaps or dips in the distribution of main belt asteroids with semi-major axis , as seen in the .... s in the asteroid belt, first recognised by Daniel KirkwoodDaniel Kirkwood Daniel Kirkwood was an American astronomer.... in 1874. The region with the densest concentration (lying between the Kirkwood gaps at 2.06 and 3.27 AU, with eccentricities below about 0.3, and inclinations smaller than 30°) is often called the Main belt. It can be further subdivided by the Kirkwood Gaps into the: Inner Main Belt, inside of the strong Kirkwood gap at 2.50 AU due to the 3:1 Jupiter orbital resonanceOrbital resonance In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influen... . The largest member is 4 Vesta4 Vesta name=4 Vesta nbsp;\| image=Vesta-HST.jpg\|4 Vesta seen by the Hubble Space Telescope in May 1996 from 177 Gm... . It apparently also includes a group called the Main Belt I asteroids which have a mean orbital radius between 2.3 AU and 2.5 AU and an inclination of less than 18°. Middle (or intermediate) Main Belt, between the 3:1 and 5:2 Jupiter orbital resonances, the latter at 2.82 AU. The largest member is 1 Ceres. This group is apparently split into the: Main Belt IIa asteroids which have a mean orbital radius between 2.5 AU and 2.706 AU and an inclination less than 33°. Main Belt IIb asteroids which have a mean orbital radius between 2.706 AU and 2.82 AU and an inclination less than 33°. Outer Main Belt between the 5:2 and 2:1 Jupiter orbital resonances. The largest member is 10 Hygiea10 Hygiea 10 Hygiea is the third largest asteroid, somewhat oblong with diameters of 350500 km and a mass estimated to be 3% of the ... . This group is apparently split into the: Main Belt IIIa asteroids which have a mean orbital radius between 2.82 AU and 3.03 AU, an eccentricity less than .35, and an inclination less than 30°. Main Belt IIIb asteroids which have a mean orbital radius between 3.03 AU and 3.27 AU, an eccentricity less than .35, and an inclination less than 30°. Other groups out to the orbit of Jupiter There are a number of more or less distinct asteroid groups outside of the Main Belt, distinguished either by mean distance from the Sun, or particular combinations of several orbital elements: Hungaria asteroids, with a mean orbital radius between 1.78 AU and 2 AU, an eccentricity less than 0.18, and inclination between 16° and 34°. Named after 434 Hungaria434 Hungaria 434 Hungaria is a relatively small Main belt asteroid.... , these are just outside Mars's orbit, and are possibly attracted by the 9:2 resonance. Phocaea asteroids, with a mean orbital radius between 2.25 AU and 2.5 AU, an eccentricity greater than 0.1, and inclination between 18° and 32°. Some sources group the Phocaeas asteroids with the Hungarias, but the division between the two groups is real and caused by the 4:1 resonance with Jupiter. Named after 25 Phocaea25 Phocaea 25 Phocaea is a Main belt asteroid.... . Alinda asteroids have a mean orbital radius of 2.5 AU and an eccentricity between 0.4 and 0.65 (approximately). These objects are held by the 3:1 resonance with Jupiter and a 4:1 resonance with EarthEarth Earth is the third planet in the solar system in terms of distance from the Sun, and the fifth largest.... . Many Alinda asteroids have perihelia very close to Earth's orbit and can be difficult to observe for this reason. Alinda asteroids are not in stable orbits and eventually will collide either with Jupiter or terrestrial planets. Named after 887 Alinda887 Alinda 887 Alinda is an asteroid orbiting the Sun.... . Pallas familyPallas family The Pallas family of asteroids is a grouping of B-type asteroids at very high inclinations in the intermediate main be... asteroids have a mean orbital radius between 2.7 and 2.8 AU and an inclination between 30° and 38°. Named after 2 Pallas2 Pallas 2 Pallas ' was the second asteroid discovered, following 1 Ceres.... . Griqua asteroids have an orbital radius between 3.1 AU and 3.27 AU and an eccentricity greater than 0.35. These asteroids are in stable 2:1 librationLibration In astronomy a libration is a very slow oscillation, real or apparent, of a satellite as viewed from the larger celestial bo... with Jupiter, in high-inclination orbits. There are about 5 to 10 of these known so far, with 1362 Griqua1362 Griqua Overview 1362 Griqua is a Outer Main-belt Asteroid discovered on July 31, 1935 by Jackson, C.... and 8373 StephengouldFacts About 8373 Stephengould 8373 Stephengould is a Outer Main-belt Asteroid discovered on January 1, 1992 by C.... the most prominent. Cybele asteroidCybele asteroid Cybele asteroids are a group of asteroids in the main belt with a mean orbital radius between 3.27 AU and 3.7 AU, an eccentr... s have a mean orbital radius between 3.27 AU and 3.7 AU, an eccentricity less than 0.3, and an inclination less than 25°. This group appears to cluster around the 7:4 resonance with Jupiter. Named after 65 Cybele65 Cybele 65 Cybele is one of the largest asteroids in the main belt.... . Hilda asteroids have a mean orbital radius between 3.7 AU and 4.2 AU, an eccentricity greater than 0.07, and an inclination less than 20°. These asteroids are in a 3:2 resonance with Jupiter. Named after 153 Hilda153 Hilda 153 Hilda is a very large asteroid orbiting in outermost Main belt.... . Thule asteroids appear to consist of only one known object, 279 Thule279 Thule 279 Thule is a very large Main belt asteroid.... , in a 4:3 resonance with Jupiter. Trojan asteroidTrojan asteroid The Trojan asteroids are a large group of objects that share the orbit of the planet Jupiter around the Sun.... s have a mean orbital radius between 5.05 AU and 5.4 AU, and lie in elongated, curved regions around the two Lagrangian pointLagrangian point Summary The Lagrangian points ; also Lagrange point, L-point, or libration point), are the five positions in inter... s 60° ahead and behind of Jupiter. The leading point, L₄, is called the 'Greek' node and the trailing L₅ point is called the 'Trojan' node, after the two opposing camps of the legendary Trojan WarTrojan War The Trojan War was a war waged, according to legend, against the city of Troy in Asia Minor , by the armies of the Achaeans,... ; with one exception apiece, objects in each node are named for members of that side of the conflict. 617 Patroclus617 Patroclus 617 Patroclus is a binary minor planet made up of two similarly-sized objects orbiting their common centre of gravity.... in the Trojan node and 624 Hektor624 Hektor 624 Hektor is the largest of the Jovian Trojan asteroids.... in the Greek node are "misplaced" in the enemy camps. There is a forbidden zone between the Hildas and the Trojans (roughly 4.05 AU to 5.0 AU). Aside from 279 Thule279 Thule 279 Thule is a very large Main belt asteroid.... and five objects in unstable-looking orbits, Jupiter's gravity has swept everything out of this region. Groups beyond the orbit of Jupiter Most of the minor planets beyond the orbit of Jupiter are believed to be composed of iceIce Ice is an Oxide class mineral that is referred to by any one of the 14 known solid phases of water.... s and other volatilesVolatiles In planetary science, volatiles, commonly called ices in the extraterrestrial context, are that group of compounds wit... . Many are similar to cometComet A comet is a small body in the solar system that orbits the Sun and exhibits a coma and/or a tail both due primarily... s, differing only in that the perihelia of their orbits are too distant from the Sun to produce a significant tail. Damocloid asteroidDamocloid asteroid Damocloids are asteroids such as 5335 Damocles and 1996 PW that have Halley family or long-period highly eccentric orbits ty... s, also known as the "Oort cloud group," are named after 5335 Damocles5335 Damocles 5335 Damocles is the archetype of the Damocloids, asteroids that are inactive nuclei of Halley Family and long period comets... . They are defined to be objects that have "fallen in" from the Oort cloudOort cloud The Oort cloud, alternatively termed the pik-Oort Cloud, is a postulated spherical cloud of comets situated about 50,... , so their aphelia are generally still out past UranusUranus Uranus is the seventh planet from the Sun.... , but their perihelia are in the inner solar system. They have high eccentricities and sometimes high inclinations, including retrograde orbits. The definition of this group is somewhat fuzzy, and may overlap significantly with comets. CentaursCentaur (planetoid) The centaurs are a class of icy planetoids named after the mythical race of centaurs.... have a mean orbital radius roughly between 5.4 AU and 30 AU. They are currently believed to be Trans-Neptunian ObjectTrans-Neptunian object A trans-Neptunian object is any object in the solar system that orbits the sun at a greater distance on average than Neptun... s that "fell in" after encounters with gas giants. The first of these to be discovered was 2060 Chiron2060 Chiron 2060 Chiron is a planetoid in the outer solar system.... . The Neptune TrojansNeptune Neptune is the eighth and outermost planet in our solar system.... currently consist of six objects: , , , , and . Trans-Neptunian ObjectTrans-Neptunian object A trans-Neptunian object is any object in the solar system that orbits the sun at a greater distance on average than Neptun... s (TNOs) are anything with a mean orbital radius greater than 30 AU. This classification includes the Kuiper Belt Objects (KBOs) and the Oort cloud. Kuiper Belt Objects extend from roughly 30 AU to 50 AU and are broken into the following subcategories: PlutinoPlutino In astronomy, a plutino is a trans-Neptunian object in 2:3 mean motion resonance with Neptune.... s are KBOs in a 2:3 resonance with Neptune, just like PlutoPluto Pluto is the second-largest known dwarf planet in the solar system.... . The perihelion of such an object tends to be close to Neptune's orbit (much as happens with Pluto), but when the object comes to perihelion, Neptune alternates between being 90 degrees ahead of and 90 degrees behind of the object, so there's no chance of a collision. The MPC defines any object with a mean orbital radius between 39 AU and 40.5 AU to be a plutino. 90482 Orcus90482 Orcus 90482 Orcus is a Kuiper Belt object that was discovered by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory... and 28978 IxionFacts About 28978 Ixion 28978 Ixion is a Kuiper belt object discovered on May 22, 2001.... are among the brightest known. CubewanoCubewano In astronomy a cubewano is a Kuiper belt object that orbits beyond Neptune and is not controlled by an orbital resonance wi... s, also known as "classical KBOs". They are named after and have a mean orbital radius between approximately 40.5 AU and 47 AU. Cubewanos are objects in the Kuiper belt that didn't get scattered and didn't get locked into a resonance with Neptune. (with two satellites) and are among the brightest. Additional groups of resonant objectsResonant trans-Neptunian object In astronomy, a resonant Trans-Neptunian Object is a Trans-Neptunian Object in mean motion orbital resonance with Neptune.... occupy other orbital resonances with Neptune than the 2:3 resonance of the plutinos and the 1:1 resonance of the Neptune Trojans (such as ), but they have not yet been officially named. There are several known objects in the 1:2 resonance, unofficially dubbed twotinos, with a mean orbital radius of 47.7 AU and an eccentricity of 0.37. There are several objects in the 2:5 resonance (mean orbital radius of 55 AU), and objects in the 4:5, 4:7, 3:5, and 3:4 resonances. Scattered Disk Objects (SDOs), unlike cubewanos and resonant objects, typically have highly inclined, high-eccentricity orbits with perihelia that are still not too far from Neptune's orbit.. They are assumed to be objects that encountered Neptune and were "scattered" out of their initial more circular, close to the ecliptic orbits. The recently famous, Pluto-size Eris belongs to this category. Extended Scattered Disk (detached) objectsDetached object (astronomy) Detached objects are nonclassical trans-Neptunian objects with a perihelion too far away from Neptune to be significantly i... with generally highly elliptical, very large orbits of up to a few hundred AU. Their perihelion is too far away from NeptuneNeptune Neptune is the eighth and outermost planet in our solar system.... for any significant interaction to occur. One typical member of the extended disk is , while some researchers include Sedna90377 Sedna 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown, Chad Trujillo and David Rabinowitz on November 14, 200... in this class. The Oort cloudOort cloud The Oort cloud, alternatively termed the pik-Oort Cloud, is a postulated spherical cloud of comets situated about 50,... is a hypothetical cloud of comets with a mean orbital radius between approximately 50,000 AU and 100,000 AU. No Oort cloud objects have been detected, the existence of this classification is only inferred from indirect evidence. Some astronomers have tentatively associated 90377 Sedna90377 Sedna 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown, Chad Trujillo and David Rabinowitz on November 14, 200... with the Oort cloud. See also Dwarf planetDwarf planet A dwarf planet is a category of celestial bodies in the solar system as introduced in a resolution by the International Astr... List of minor planetsList of minor planets * List of asteroids* List of comets* List of trans-Neptunian objects... Minor Planet CenterMinor Planet Center The Minor Planet Center operates at the Smithsonian Astrophysical Observatory, which is part of the Center for Astrophysics ... MesoplanetMesoplanet Mesoplanet is a term coined by Isaac Asimov to refer to planetary bodies with sizes smaller than Mercury but larger than 1 C...