Minor planets, or asteroids or planetoids, are minor celestial bodies of the Solar system orbiting the Sun (mostly Small solar system bodies) that are smaller than major planets, but larger than meteoroids (commonly defined as being 10 meters across or less^[1]), and that are not comets. The distinction is made on visual appearance when discovered: comets must show a perceptible coma, and they get listed in their own catalogs. Minor planets in contrast appear star-like ("asteroid", ancient Greek Aστήρ, astēr = star); they get a provisional designation by year in the order of discovery, and a designation (a sequential number) and name if their existence is well established and an orbit has been determined. Their physical nature often remains poorly known. Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... The Sun is the star at the center of the Solar System. ... It has been suggested that minor planet be merged into this article or section. ... The eight planets and three dwarf planets of the Solar System. ... Look up meteoroid in Wiktionary, the free dictionary. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... The comet Ikeya-Zhang exhibiting a bright, condensed coma (march 2002) In astronomy, the nebulous envelope around the nucleus of a comet is called its coma (from the Latin word for hair). It is formed when the comet passes close to the sun on its highly elliptical orbit; as the... This article is about the astronomical object. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ...

The first named minor planet was Ceres, discovered in 1801 by Giuseppe Piazzi which was originally considered a new planet, and is now classified as a dwarf planet. Sir William Herschel (discoverer of Uranus), coined the term asteroid for the first objects discovered in the 19th century, all of which orbit the sun between Mars and Jupiter, and generally in relatively low-eccentricity (i.e., not very elongated) orbits. But since then, minor planets have been found to cross the orbits of planets, from Mercury to Neptune -- with hundreds of trans-Neptunian objects (TNOs) now known to exist well past Neptune's orbit. 1 Ceres (IPA , Latin: ) is a dwarf planet in the asteroid belt. ... Giuseppe Piazzi. ... Artists impression of Pluto (background) and Charon (foreground). ... Sir Wilhelm Friedrich Herschel (November 15, 1738 Hanover - August 25, 1822 Windsor) was a German-born astronomer and composer who became famous for discovering the planet Uranus, and made many other astronomical discoveries. ... Adjectives: Uranian Atmosphere Surface pressure: 120 kPa (at the cloud level) Composition: 83% Hydrogen 15% Helium 1. ... 253 Mathilde, a C-type asteroid. ... Note: This article contains special characters. ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% H2 ~13% Helium 0. ... Note: This article contains special characters. ... Note: This article contains special characters. ...

Though the main distinction between a minor planet and a comet lies in the fact that comets show a coma (or atmosphere) and/or a tail, due primarily to sublimation of ices by solar radiation, one can justifiably consider comets to be a subset of the large group known as minor planets. A few objects have ended up being dual-listed because they were first classified as minor planets but later showed evidence of cometary activity. Conversely, some (perhaps all) comets eventually are depleted of their volatile ices and then appear as pointlike objects, i.e. asteroids. The outermost regions of the solar system are also believed to contain a cloud of dormant comets, and the closer Trans-neptunian objects that have been discovered may not be fundamentally different from giant proto-comets. This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ...

Minor planets are divided into groups and families based on their orbital characteristics. Apart from the broadest divisions, it is customary to name a group of asteroids after the first member of that group to be discovered (often the largest). While so-called groups are relatively loose dynamical associations, families are much "tighter" and result usually from the catastrophic breakup of a large parent asteroid sometime in the past. Families have only been recognized within the main asteroid belt. They were first recognised by Kiyotsugu Hirayama in 1918 and are often called Hirayama families in his honor. Minor planet is the official term for asteroids and trans-Neptunian objects. ... The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. ... Kiyotsugu Hirayama (平山清次) (1874–1943) was a Japanese astronomer, best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called Hirayama families in his honour. ... A Hirayama family of asteroids is a group of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination. ...

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 asteroids are hypothetical asteroids with an aphelion less than 0.4 AU, ie, they orbit entirely within the orbit of Mercury. A few searches for Vulcanoids have been conducted but there have been none discovered so far.
• Apoheles are asteroids whose aphelion is less than 1 AU, meaning they orbit entirely within Earth's orbit. "Apohele" is Hawaiian for "orbit". Other proposed names for this group are Inner-Earth Objects (IEOs) and Anons (as in "Anonymous"). As of May 2004 there are only two known Apoheles: 2003 CP₂₀ and 2004 JG₆.
• Mercury-crosser asteroids having a perihelion smaller than Mercury's 0.3075 AU.
• Venus-crosser asteroids having a perihelion smaller than Venus'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 asteroids having a perihelion smaller than Earth's 0.9833 AU. This group includes the above Mercury- and Venus-crossers, apart from the Apoheles. They are also divided into the
  • Aten asteroids having a semi-major axis less than 1 AU, named after 2062 Aten.
  • Apollo asteroids having a semi-major axis greater than 1 AU, named after 1862 Apollo.
• Arjuna asteroids 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 Apohele, Amor, Apollo or Aten groups can also be classified as Arjunas. The term was introduced by Spacewatch and does not refer to an existing asteroid; examples of Arjunas include 1991 VG.
• Earth Trojans are asteroids located in the Earth-Sun Lagrangian points 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 asteroids 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 asteroids.

Vulcanoids are hypothetical asteroids that may orbit in a dynamically stable zone between 0. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... Note: This article contains special characters. ... Apohele asteroids are a subclass of Aten asteroids. ... 2004 : January - February - March - April - May - June - July - August - September - October - November - December Deaths in May • 28 Gerald Anthony • 27 Umberto Agnelli • 22 Richard Biggs • 20 Len Murray • 17 Tony Randall • 17 Ezzedine Salim • 9 Alan King • 9 Akhmad Kadyrov • 8... Discovered February 11, 2003, by the Lincoln Near-Earth Asteroid Research projects station at Socorro, New Mexico, 2003 CP20 (also written 2003 CP20), was the first asteroid known to have an orbit entirely within that of Earth. ... 2004 JG6 (also written 2004 JG6) is an unusual asteroid. ... A Mercury-crosser asteroid is an asteroid whose orbit crosses that of Mercury. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... A Venus-crosser asteroid is an asteroid whose orbit crosses that of Venus. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ... An Earth-crosser asteroid is a Near-Earth asteroid whose orbit crosses that of Earth. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976 by Eleanor F. Helin). ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... 2062 Aten is an asteroid that was discovered at the Palomar Mountain Observatory by Eleanor F. Helin, who is now the principal scientist for the NEAT (Near-Earth Asteroid Tracking) project. ... The Apollo asteroid 25143 Itokawa. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... 1862 Apollo is a Q-type asteroid, discovered by Karl Reinmuth in 1932, but lost and not recovered until 1973. ... The Arjuna asteroids are a class of near-Earth asteroids whose orbits are very Earth-like in character, having low inclination, orbital periods close to one Earth year, and low eccentricity. ... Apohele asteroids are a subclass of Aten asteroids. ... The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor. ... The Apollo asteroid 25143 Itokawa. ... The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976 by Eleanor F. Helin). ... A contour plot of the effective potential of a two-body system (the Sun and Earth here), showing the five Lagrange points. ... Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earths orbit. ... The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor. ...

Groups out to the orbit of Mars

• The Amor asteroids, named after 1221 Amor are Near-Earth asteroids that are not Earth-crossers, having a perihelion just outside the Earth's orbit.
• Mars-crosser asteroids have orbits that cross that of Mars, but do not necessarily closely approach the Earth's.
• Mars Trojans follow or lead Mars on its orbit, at either of the two Lagrangian points 60° ahead (L₄) or behind (L₅). The only one known is 5261 Eureka. The Minor Planet Center has not listed any Mars trojans with confirmed orbits,^[2] for controversial reasons.
• Many of the Earth- Venus- and Mercury-crosser asteroids have aphelia greater than 1AU.

The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor. ... 1221 Amor is the namesake of the Amor asteroids, a group of near-Earth asteroids whose orbits range between those of Earth and Mars. ... Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earths orbit. ... An Earth-crosser asteroid is a Near-Earth asteroid whose orbit crosses that of Earth. ... A Mars-crosser asteroid is an asteroid whose orbit crosses that of Mars. ... A contour plot of the effective potential of a two-body system (the Sun and Earth here), showing the five Lagrange points. ... 5261 Eureka was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Trojan asteroid. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ...

The main asteroid belt

Main article: Asteroid belt

The overwhelming majority of known asteroids have orbits lying between the orbits of Mars and Jupiter, roughly between 2 to 4 AU. These could not form a planet due to the gravitational influence of Jupiter. Jupiter's gravitational influence, through orbital resonance, clears Kirkwood gaps in the asteroid belt, first recognised by Daniel Kirkwood in 1874. For details on the physical properties of bodies in the asteroid belt see Asteroid and Main-belt comet. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... The astronomical unit (AU or au or a. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Kirkwood gaps are gaps that appear in a graph if we classify the asteroids according to their periods, which is proportional to their mean radius from the Sun. ... Daniel Kirkwood (September 27, 1814 - June 11, 1895) was an American astronomer. ... Year 1874 (MDCCCLXXIV) was a common year starting on Thursday (link with display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day slower Julian calendar). ...

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: In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. ...

• Inner Main Belt, inside of the strong Kirkwood gap at 2.50 AU due to the 3:1 Jupiter orbital resonance. The largest member is 4 Vesta.
  • 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 Hygiea. 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°.

In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... 4 Vesta (ves-ta) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. ... 1 Ceres (IPA , Latin: ) is a dwarf planet in the asteroid belt. ... 10 Hygiea (hye-jee-a or hi-jee-a) is the fourth largest Main belt asteroid with a diameter of 407 km. ...

Families within the main asteroid belt

Main article: Asteroid family

About 30% to 35% of the bodies in the main belt belong to dynamical families each thought to have a common origin in a past collision between asteroids. A list can be found here. Minor planet is the official term for asteroids and trans-Neptunian objects. ... Minor planet is the official term for asteroids and trans-Neptunian objects. ...

Asteroid groups out to the orbit of Jupiter. The main belt is shown in red

Image File history File links Download high resolution version (1201x901, 44 KB) Summary Plot of inclination vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ... Image File history File links Download high resolution version (1201x901, 44 KB) Summary Plot of inclination vs semi-major axis for numbered asteroids inward of about 6 AU. The main belt region is shown in red, and contains 93. ...

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 Hungaria, 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 Phocaea.
• 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 Earth. 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 Alinda. 434 Hungaria is a relatively small Main belt asteroid. ... 25 Phocaea (foe-see-É™, fÉ™-see-É™ (key)) is a Main belt asteroid. ... The Alinda asteroids are a group of asteroids with a semi-major axis of about 2. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... 887 Alinda 887 Alinda is an asteroid orbiting the Sun. ...

• Pallas family asteroids have a mean orbital radius between 2.7 and 2.8 AU and an inclination between 30° and 38°. Named after 2 Pallas.
• 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 libration with Jupiter, in high-inclination orbits. There are about 5 to 10 of these known so far, with 1362 Griqua and 8373 Stephengould the most prominent.
• Cybele asteroids 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 Cybele.
• 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 Hilda.
• Thule asteroids appear to consist of only one known object, 279 Thule, in a 4:3 resonance with Jupiter.
• Trojan asteroids have a mean orbital radius between 5.05 AU and 5.4 AU, and lie in elongated, curved regions around the two Lagrangian points 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 War; with one exception apiece, objects in each node are named for members of that side of the conflict. 617 Patroclus in the Trojan node and 624 Hektor 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 Thule and five objects in unstable-looking orbits, Jupiter's gravity has swept everything out of this region. The Pallas family of asteroids is a grouping of B-type asteroids at very high inclinations in the intermediate main belt (Cellino et al (2002)). The namesake is 2 Pallas, an extremely large asteroid with a mean diameter of about 530 km. ... 2 Pallas (pal-us, Greek Παλλάς) was the first asteroid discovered after 1 Ceres. ... The animation shows a set of simulated views of the Moon over one month, like a picture taken at the same time each day. ... 65 Cybele (sib-a-lee) is one of the largest asteroids in the main belt. ... 65 Cybele is one of the largest asteroids in the main belt. ... Hilda asteroids are asteroids with a semi-major axis between 3. ... 153 Hilda is an very large asteroid orbiting in outermost Main belt. ... 279 Thule is a very large Main belt asteroid. ... 279 Thule is a very large Main belt asteroid. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... A contour plot of the effective potential of a two-body system (the Sun and Earth here), showing the five Lagrange points. ... The fall of Troy by Johann Georg Trautmann (1713–1769) From the collections of the granddukes of Baden, Karlsruhe The Trojan War was waged, according to legend, against the city of Troy in Asia Minor, by the armies of the Achaeans (Mycenaean Greeks), after Paris of Troy stole Helen from... 617 Patroclus is the second Jovian Trojan asteroid to be discovered. ... 624 Hektor is the largest of the Jovian Trojan asteroids. ... 279 Thule is a very large Main belt asteroid. ...

Groups beyond the orbit of Jupiter

Most of the minor planets beyond the orbit Jupiter are believed to be composed of ices and other volatiles. Many are similar to comets, differing only in that the perihelia of their orbits are too distant from the Sun to produce a significant tail. Snowflakes by Wilson Bentley, 1902 Ice is the name given to any one of the 14 known solid phases of water. ... Look up volatile in Wiktionary, the free dictionary. ... Comet Hale-Bopp Comet McNaught as seen from Swifts Creek, Victoria, Australia on 23 January 2007 A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...

• Damocloid asteroids, also known as the "Oort cloud group," are named after 5335 Damocles. They are defined to be objects that have "fallen in" from the Oort cloud, so their aphelia are generally still out past Uranus, 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.
• Centaurs have a mean orbital radius roughly between 5.4 AU and 30 AU. They are currently believed to be Trans-Neptunian Objects that "fell in" after encounters with gas giants. The first of these to be discovered was 2060 Chiron.
• The Neptune Trojans currently consist of four objects: 2001 QR₃₂₂, 2004 UP₁₀, 2005 TN₅₃, and 2005 TO₇₄.
• Trans-Neptunian Objects (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:
    • Plutinos are KBOs in a 2:3 resonance with Neptune, just like Pluto. 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 Orcus and 28978 Ixion are among the brightest known.
    • Cubewanos, also known as "classical KBOs". They are named after (15760) 1992 QB₁ 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. (136108) 2003 EL₆₁ (with two satellites) and (136472) 2005 FY₉ are among the brightest.
    • Additional groups of resonant objects 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 2001 QR₃₂₂), 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, they have typically 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) objects with generally highly elliptical, very large orbits of up to a few hundred AU. Their perihelion is too far away from Neptune for any significant interaction to occur. The recently discovered 2000 CR₁₀₅ is a typical member of the extended disk, while some researchers^[3] include Sedna in this class.
  • The Oort cloud 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 Sedna with the Oort cloud.

Damocloids are asteroids such as 5335 Damocles and 1996 PW that have long-period highly eccentric orbits typical of periodic comets such as 1P/Halley, but without showing a cometary coma or tail. ... 5335 Damocles is the archetype of the Damocloids, astroids that are inactive nuclei of Halley Family and long period comets. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... This article is about retrograde motion. ... The centaurs are a class of icy planetoids that orbit the Sun between Jupiter and Neptune, named after the mythical race of centaurs. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ... 2060 Chiron (IPA: ) is an object in the outer solar system with an orbit between those of Saturn and Uranus and a radius of 71±5 km [1]. Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet. ... Note: This article contains special characters. ... 2001 QR322 (also written 2001 QR322) is an asteroid discovered in 2001 that is one of the two currently known Trojan asteroid of Neptune (the other is 2004 UP10). ... 2004 UP10 is a Trojan asteroid of Neptune, and one of only two known. ... 2005 TN53 (also written 2005 TN53) is a possible Trojan asteroid of Neptune which was discovered by Scott S. Sheppard and Chadwick A. Trujillo in 2005. ... 2005 TO74 (also written 2005 TO74) is a possible Trojan asteroid of Neptune which was discovered by Scott S. Sheppard and Chadwick A. Trujillo in 2005. ... A trans-Neptunian object (TNO) is any object in the solar system that orbits the sun at a greater distance on average than Neptune. ... The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ... In astronomy, a plutino is a trans-Neptunian object that has a 3:2 orbital resonance with Neptune. ... Atmospheric characteristics Atmospheric pressure 0. ... 90482 Orcus (originally known by the provisional designation 2004 DW) is a Kuiper Belt object (KBO) that was discovered by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. ... (28978) Ixion (ik·sye·un) is a Kuiper belt object discovered on May 22, 2001 with a diameter of < 822 km and a semimajor axis of about 39. ... A cubewano is any substantial Kuiper belt object, orbiting beyond about 41 AU and not controlled by resonances with the outer planets. ... (15760) 1992 QB1 (also written (15760) 1992 QB1) was the first trans-Neptunian object to be discovered after Pluto and Charon. ... (136108) 2003 EL61 (also written (136108) 2003 EL61), is a large (roughly one-third the mass of Pluto) and very unusual Kuiper belt object discovered by Mike Brown at Caltech in the United States. ... (136472) 2005 FY9 (also written (136472) 2005 FY9) is a very large Kuiper belt object discovered on March 31, 2005 by the team led by Michael Brown. ... In astronomy, a resonant Trans-Neptunian Object is a Trans-Neptunian Object (TNO) in mean motion orbital resonance with Neptune. ... 2001 QR322 (also written 2001 QR322) is an asteroid discovered in 2001 that is one of the two currently known Trojan asteroid of Neptune (the other is 2004 UP10). ... A scattered disk object (or scattered disc object or SDO) is a trans-Neptunian object of the Kuiper belt with a very eccentric orbit. ... Eris (IPA or ), officially designated 136199 Eris, is the largest known dwarf planet in the solar system. ... Note: This article contains special characters. ... 2000 CR105 is the third most distant known object in the solar system after 2003 UB313 and 90377 Sedna. ... 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... 90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ...

Quasi-satellites and "horseshoe objects"

Some asteroids have unusual horseshoe orbits that are co-orbital with the Earth or some other planet. Examples are 3753 Cruithne and 2002 AA₂₉. The first instance of this type of orbital arrangement was discovered between Saturn's moons Epimetheus and Janus. A horseshoe orbit is the type of orbit you get when you observe an object from another nearly co-orbital object, such as a planet. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... 3753 Cruithne (English krew-een-yÉ™; Modern Irish krin-nyÉ™) is an asteroid in orbit around the Sun. ... Asteroid 2002 AA29 (also written 2002 AA29) is a near-Earth asteroid discovered in January 2001 by the LINEAR asteroid survey. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Epimetheus (ep-i-mee-thee-us, Greek Επιμηθεύς) is a moon of Saturn. ... Janus (jay-nus, Greek Ιανός) is a moon of Saturn. ...

Sometimes these "horseshoe objects" temporarily become quasi-satellites for a few decades or a few hundred years, before returning to their prior status. Both Earth and Venus are known to have quasi-satellites. Diagram of generic quasi-satellite orbit A quasi-satellite is an object similar to a planet or satellite of the Sun, however its orbit encompasses its planet and the planets star. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ...

Such objects, if associated with Earth or Venus or even hypothetically Mercury are a special class of Aten asteroids. However, such objects could be associated with outer planets as well. Note: This article contains special characters. ... The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976 by Eleanor F. Helin). ...

See also

• Asteroid
• Minor Planet Center
• List of minor planets
• Mesoplanet

253 Mathilde, a C-type asteroid. ... The Minor Planet Center operates at the Smithsonian Astrophysical Observatory (SAO), which is part of the Center for Astrophysics (CfA) along with the Harvard College Observatory (HCO). ... List of asteroids List of comets See also Trans-Neptunian object Categories: Solar System ... Mesoplanet is a term coined by Isaac Asimov to refer to planetary bodies with sizes smaller than Mercury but larger than 1 Ceres. ...

References and external links

1. ^ Beech, M.; Steel, D. I. (September 1995). "On the Definition of the Term Meteoroid". Quarterly Journal of the Royal Astronomical Society 36 (3): 281–284. Retrieved on 2006-08-31. 
2. ^ http://cfa-www.harvard.edu/iau/lists/MarsTrojans.html
3. ^ http://www.obs-nice.fr/gladman/cr105.html

• Committee on Small Body Nomenclature
• List of minor planet orbital groupings and families from ProjectPluto
• Cunningham, Clifford, "Introduction to Asteroids: The Next Frontier", ISBN 0-943396-16-6
• James L. Hilton: When Did the Asteroids Become Minor Planets?
• Kirkwood, Daniel; Relations between the Motions of some of the Minor Planets (1874).
• Schmadel, L.D. (2003). Dictionary of Minor Planet Names. 5th ed. IAU/Springer-Verlag: Heidelberg.
• Large amount of information on asteroid groups collected by Gérard Faure, translation Richard Miles.