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Solar System Scratchpad

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List of dwarf planets in the solar system.

Official Dwarf Planets[]

  • Ceres - First body in the asteroid belt discovered, at first thought to be the eight planet, then redesignated the largest asteroid, and later a dwarf planet due to its roundness. It is the only dwarf planet in the asteroid belt. Composed mainly of water ice. Second destination for the Dawn spacecraft.
  • Pluto - Discovered after an extensive search for Planet X. Initially thought to be Earth size and dubbed the ninth planet, then continuously reduced in size as its brightness became clear and its large moon was discovered, until another object Eris was discovered in its region of space that was more massive than it, when it was demoted to a Dwarf Planet status. Considered by some a double dwarf planet due to its large moon. Also has three tiny moons and could support a ring system. First Kuiper Belt object discovered, in 2:3 orbital resonance with Neptune. Target of New Horizons spacecraft. Its surface may contain organics.
  • Eris - The second dwarf planet found in the Kuiper Belt, briefly referred to as the 10th planet. Being more massive than Pluto and about the same size, Eris' discovery lead to a new definition of the word planet and reclassified itself, Pluto, and Ceres and Dwarf Planets. Originally designated 2003 UB313 and codenamed "Xena", it is now named after the Greek goddess of discord. Furthest body detected at time of discovery, when it was near its aphelion, nearly three times as far as Pluto. Much more dense than Pluto (and thus composed of more rock) and further away, but has about the same surface composition. Largest scattered disc object, which depending on the definition used, would also be the largest Kuiper Belt object. Color appears greyish, unlike Pluto, because it is far enough for Methane to condense on all parts of its surface, including low albedo features. Like Pluto, and unlike other large KBOs, it has Methane on its surface. Currently has no atmosphere. Its albedo is greater than freshly fallen snow, and one of the most reflective known objects in the Solar System. Has one small moon, Dysnomia, which allowed its mass to be computed as a 27% greater than Pluto's. Its size became better known than Pluto's temporarily in 2011, at 2326 km +/- 12 km, but was found to be slightly smaller when Pluto's size was remeasured. Its atmosphere may return when it gets closer, possibly revealing a patchy surface like Pluto's.
  • Haumea - Fifth dwarf planet recognized, originally called 2003 EL61. Discovery claimed by two teams, one was able to claim discovery, while another to name the object. Originally code named Santa, now named after a goddess, whose body was broken up to form the Hawaiian island. Though to have broken up 4.5 BYA and formed two satellites (made of pure water ice), in addition to a family that shares its orbit (some of which became comets), the first such family found in the Kuiper Belt. Its satellites are unusual in that they are not coplanar. Originally classified as a classic Kuiper Belt object, it has now been shown to be in 7:12 orbital resonance with Neptune. In a highly inclined orbit similar to Makemake and the third apparent brightest body in the Kuiper Belt. Spins so fast (4 hours), that it is shaped somewhat like a cigar, yet remains in hydrostatic equilibrium. Likely mostly rock with a thin layer of water ice, unusual in that it doesn't show signs of Methane. Surface is mottled, with a large red spot high in organics, possibly a crater, though not as extreme as Pluto. Its surface appears to by crystalline ice, which is caused by tidal forces with its moon and radiogenic elements.
  • Makemake - Largest object in the Classical Kuiper Belt (dynamically hot) and third largest dwarf planet, three quarters or as big as Pluto. Second apparent brightest Kuiper Belt object in the solar system, it escaped detection for a while due to its high inclined orbit and because it was at its furthest point when discovered. The only undetected Dwarf Planet that Clyde Thombough could have detected, though it was near the galactic plain at the time. Originally named 2005 FY9 and code named Easterbunny, officially named after a creator and fertility god of Easter Island. Located in the center of the Kuiper Belt. Reddish in color, surface likely composed of frozen methane. Has no moons. Surprisingly found to have no significant atmosphere during an occultation.

Prime Dwarf Planet Candidates[]

Mike Brown's List:

  • Orcus - Originally 2004 DW, the largest Plutino after Pluto. Thought of as the "anti-Pluto" because it is at perihelion when Pluto is at aphelion and vice versa. It also has a similarly large in ratio moon. Named after Pluto's Etruscan equivalent, while its moon is named after the one who ferried souls to the underworld, Vanth. It was the thought to be the largest TNO at discovery (after Quaoar), and now thought to be almost certainly a dwarf planet by Mike Brown.
  • 2002 MS4 - Ss:2002 MS4
  • Salacia - Ss:Salacia
  • Quaoar - Dwarf planet candidate orbiting, 1070 km in diameter, and somewhat elongated. Largest KBO found since Pluto. Furthest out object resolved by a telescope when Hubble measured its size, and the first trans-neptunian object directly measured. Given the minor planet number 50000. Has a small moon. First KBO found larger than Ceres. Sedna was briefly thought to be the largest KBO found, but after it was displaced by Eris, Quaor was found to be larger (larger than Ceres, but smaller than Charon, though more massive), and most likely a dwarf planet. The largest dynamically cold Cubewano (smaller than Makemake, which is hot), has exceptionally low eccentricity and inclination for a Plutoid. Unusual in that it is red and has water ice on it, like a smaller version of "2007 OR10" which has already lost all of its atmosphere. Its surface was likely recently resurfaced by volcanism or an impact, suggested by the detection of ammonia hydrate and crystalline water.
  • 2007 OR10 - Currently the largest solar system body without an official name. Tops Mike Brown's list of objects most certainly dwarf planets, and the fifth largest dwarf planet. About half its surface is covered in water ice that once spewed from ancient geysers. Nicknamed "Snow White", because it was once thought to have been a piece knocked off of Haumea and presumed white (and the "seventh dwarf" found by Mike Brown's team), it is actually one of the reddest objects known in the solar system. May be covered in a thin layer of methane, remnants of a condensed atmosphere. Spectrum is similar to the smaller Quauar, which also is red with water ice, and lost all its atmosphere to space. This object has almost lost all of its atmosphere. A scattered disk object in 3:10 resonance with Neptune, and currently the second furthest out known other than Eris.
  • Sedna - Dwarf planet candidate orbiting in a detached orbit around the Sun, possibly the first Inner Oort Cloud object discovered. Orbit is not affected by Neptune. Detached objects with perihelions greater than 75AU have been dubbed "Sednoids" after the discovery of the second one. Could be indicative of stars effects when they were much closer than they are today when the Sun was still in a cluster. Alternatively, the fact its eccentricity has not reduced over time could point to a present day star in the Solar System. It could also be a captured dwarf planet from another star, or have been moved by a passing star. Its year is 12,000 years and size thought to be two thirds that of Pluto's. It will reach perihelion in 72 years. Its rotation was initially thought to be the slowest in the Solar System other than Venus or Mercury, which was thought to be due to a close moon, but none have been found. It was later found to have a rather typical period of 10 hours. Its name was announced before it was confirmed and numbered, but the IAU allowed it to be used officially. It is one of the reddest objects known in the solar system. It was the furthest object found prior to the discovery of Eris. When discovered, was the largest body beyond discovered since Pluto, half way between Quaoar and Pluto.


  • 2012 VP113 - Second Inner Oort Belt object discovered. Likely a dwarf planet with half the size of Sedna. Its perihelion is only the second found to be far enough so as not to be affected by Neptune, and is thus "detached" from the main part of the Solar System. Its argument of perihelion is near Sedna's, which could be signs of herding from a more distant super-Earth planet. Its origin could be a planet that was first scattered from the solar system, and then its perihelion reduced by other stars in the Sun's birth cluster. It would then have been unaffected by the planets or passing nearby stars, and thus remained stable over billions of years. Nicknamed "Biden" after the "VP" portion of its designation. Its surface is likely pink in color, indicative of forming in the gas giant region of space rather than the Kuiper Belt.
  • Huya - Ss:Huya
  • Ixion - The most intrinsically bright one found at the time of its discovery in 2001. Thought to be larger than Ceres and Charon, and the largest KBO known, but now only 650 km, smaller than the previously largest known KBO Varuna, but still large enough to probably be a dwarf planet. Originally thought to be in 3:4 resonance, it is now considered a Plutino with 2:3 resonance. Currently, the fifth largest Plutino.
  • Varuna - Ss:Varuna
  • 1996 TL66 - Large scattered disk object, the largest Kuiper Belt Object known at the time of its discovery. At the time, said to have the surface area of Texas. The object categorized as scattered disk object discovered and first to be found that goes that far out (varies from Pluto-like to three times Pluto's distance), in what was thought a no man land, located near its perihelion. Another object was found earlier though, but only later recognized as being in the scattered disk. Probably a dwarf planet according to Mike Brown.
  • 2002 AW197 - Probable dwarf planet cubewano located at in the edge of the Kuiper Belt. Thought to be one of the largest KBOs found (2/3 Pluto's size) before Eris. It was found to be much more reflective than expected (18%), thus smaller than Ceres. This made it possible that Pluto could be much larger in comparison to most KBOs than thought. It was later found to be larger by the Spitzer, 734 km. It is red with no sign of water ice. Mike Brown considers it highly likely to be a dwarf planet.
  • 2002 TC302 - Ss:2002 TC302
  • 2010 EK139 - One of three dwarf-planet sized objects found during a comprehensive search of the Kuiper Belt in 2010.
  • 2010 KZ39 - One of three dwarf-planet sized objects found during a comprehensive search of the Kuiper Belt in 2010.
  • 2010 FX86 - One of three dwarf-planet sized objects found during a comprehensive search of the Kuiper Belt in 2010.