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Composite exaggerated-color image of Pluto and its moon Charon.Separation not to scale 4 Vesta, an asteroid that was once a dwarf planet [4]. Starting in 1801, astronomers discovered Ceres and other bodies between Mars and Jupiter that for decades were considered to be planets.
Many TNOs are often just assumed to have Pluto's density of 2.0 g/cm 3, but it is just as likely that they have a comet-like density of only 0.5 g/cm 3. [ 4 ] For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 ...
Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the middle main asteroid belt between the orbits of Mars and Jupiter. It was the first known asteroid , discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical Observatory in Sicily , and announced as a new planet .
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than Eris.
Since Pluto's reclassification as a dwarf planet in 2006 by the International Astronomical Union (IAU), space exploration has increasingly focused on these celestial bodies. In 2015 significant milestones in dwarf planet exploration were reached with the flybys of Pluto and Ceres by the New Horizons and Dawn spacecraft .
The catalog's first object is 1 Ceres, discovered by Giuseppe Piazzi in 1801, while its best-known entry is Pluto, listed as 134340 Pluto. The vast majority (97.3%) of minor planets are asteroids from the asteroid belt (the catalog uses a color code to indicate a body's dynamical classification).
Many TNOs in the size range of about 400–1000 km have oddly low densities, in the range of about 1.0–1.2 g/cm 3, that are substantially less than those of dwarf planets such as Pluto, Eris and Ceres, which have densities closer to 2. Brown has suggested that large low-density bodies must be composed almost entirely of water ice since he ...
Dwarf planets, other than Ceres, are plutoids that have elliptical orbits: [25] [26] [27] Ceres, 2.8 AU in the asteroid belt; Orcus 39.4 AU, Trans-Neptunian-Kuiper belt object; Pluto 39 AU, Kuiper belt (a planet until 2006) Haumea 43 AU, Kuiper belt; Makemake 45.8 AU, Kuiper belt; Eris 95.6 AU, Kuiper belt; Gonggong Scattered disc object, 34 to ...