90482 Orcus This means that Orcus is currently viewed pole-on, which could explain the near absence of any rotational modulation of its brightness. If, however, the primary is tidally locked with the satellite, the rotational period will coincide with the 9.7-day orbital period of Vanth. This minor planet was named after one of the Roman gods of the underworld, Orcus. While Pluto was the ruler of the underworld, Orcus was a punisher of the damned. The approved naming citation was published by the Minor Planet Center on 26 November 2004 (). Under the guidelines of the International Astronomical Union's (IAU) naming conventions,
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