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90482 Orcus, 2004 DW

Potential Dwarf Planet of the Solar System

A distant object belonging to the class known as plutinos, bodies the follow orbits of the kind typified by Pluto. Like Pluto, Orcus follows an eccentric orbital path around the Sun that carries it well outside the plane of the Solar System, and (also like Pluto) it completes each orbit in just under 250 years (specifically 245 years, compared with 247 for Pluto). The angle of its orbit relative to the Sun is quite different from Pluto's, however, and the two dwarf planets do not approach either closely.

Orcus is presently close to its aphelion, the farthest point in its orbit from the Sun. From that point, in the year 2019, its path will carry it on its long journey back inward through the Solar System. Like Pluto, at its closest point it will spend some years slightly closer to the Sun than the planet Neptune.

Estimates of Orcus' size vary slightly, but it has a diameter of about 800km, making it considerably smaller than Pluto. Unusually for a body of this kind, much of its surface is covered with crystalline water ice, presumably due to the action of cryovolcanoes expelling frozen water onto its surface. It has a single known satellite, Vanth, which approaches half the diameter of Orcus (or perhaps even exceeds it - the sizes of these two bodies are not known exactly). The names of Orcus and its moon Vanth both come from Etruscan mythology, where they belonged to a god and goddess of the underworld.


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