90482 Orcus 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 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
90482 Orcus with the normal object naming procedures. Vanth was found at 0.25 arcsec from Orcus with magnitude difference of . Estimates made in 2009 by Mike Brown show that the apparent magnitude of Vanth is which is magnitudes fainter than Orcus. Assuming equal albedos this would mean a diameter of 280 km, or 2.9 times smaller than the primary. However, the dissimilar colors of Orcus (neutral) and Vanth (red) suggest that Vanth could have an albedo a factor of two lower than Orcus. Should Vanth have an albedo of only 0.12, Vanth could be as large as 380 km with Orcus