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 relatively large satellite (Vanth, see below) may change them considerably. The absolute magnitude of Vanth is estimated at 4.88, which means that it is about 11 times fainter than Orcus itself. If the albedos of both bodies are the same at 0.23 then the size of Orcus is about , and the size of Vanth is about . The ALMA submillimeter measurements taken in 2016 showed that Vanth has a relatively large size of with albedo of about 8% while Orcus' has a slightly smaller size of 910 km. Using a stellar occultation by Vanth in 2017, Vanth's diameter has