90482 Orcus - Satellite

Satellite

Using observations with the Hubble Space Telescope from November 13, 2005, Mike Brown and T.A. Suer detected a satellite. The discovery of a satellite of Orcus was reported in IAUC 8812 on 22 February 2007. The satellite was given the designation S/2005 (90482) 1 before later being named Vanth. It orbits Orcus in a nearly face-on circular orbit with an eccentricity of about 0.007, and an orbital period of 9.54 days. Vanth orbits only 9030 ± 89 km from Orcus and is too close to Orcus for ground-based spectroscopy to determine the surface composition of the satellite.

Mike Brown suspects that like the Pluto–Charon system, Orcus and Vanth are tidally locked. Vanth does not resemble known collisional satellites because its spectrum is very different from that of its primary, and it may be a captured KBO. Vanth could also have originated as a result of rotational fission of the primordial Orcus, which would have rotated much faster than now.

On March 23, 2009, Brown asked readers of his weekly column to suggest possible names for the satellite, with the best one to be submitted to the International Astronomical Union (IAU) on April 5. The name Vanth, after the Etruscan goddess who guided the souls of the dead to the underworld, was eventually chosen from among a large pool of submissions. This submission will be assessed by the IAU's Committee for Small Body Nomenclature, which will vote on whether to approve it, in accordance with the normal object naming procedures.