90482 Orcus is a Kuiper Belt object (KBO) that was discovered by Michael (Mike) E. Brown of Caltech, Chadwick (Chad) A. Trujillo of the Gemini Observatory, and David L. Rabinowitz of Yale University. The image of this object was first acquired on February 17, 2004.

Size and magnitude

The apparent magnitude of the object is 18.5, which is the same brightness as 50000 Quaoar. The orbit indicates that the object is a Plutino. Therefore, the object is probably larger than Quaoar, since it is farther from the Sun. Using an assumed albedo of 0.09, Trujillo estimates its diameter to be approximately 1600 km, which makes Orcus potentially the second-largest KBO, after Pluto. (The recently discovered 90377 Sedna, lying beyond the Kuiper Belt, may be the second-largest TNO).

Name

Since it shares a similar size and orbit to that of Pluto, it too must be named after a deity of the underworld. In accordance with IAU rules, the discoverers' suggested name of Orcus was approved and published November 22, 2004. Orcus is both another name for the Greek deity Hades and a separate god of the dead in Roman mythology.

External links and sources

• MPEC 2004-D09 announcing the discovery but attributing it to Raymond J. Bambery , Steven H. Pravdo , Michael D. Hicks , Kenneth J. Lawrence, Daniel MacDonald , Eleanor F. Helin and Robert Thicksten / NEAT
• MPEC 2004-D13 correcting MPEC 2004-D09
• C. Trujillo's page on 2004 DW
• First BBC article
• First New Scientist article