On 16 May 2010 around 06:00 -- 06:15 UT (beginning of night of Saturday, May 15th, as seen from N. America and Hawaii, beginning of night of Sunday, May 16th, as seen from New Zealand) the Trans-Neptunian-Object Orcus and its satellite Vanth may occult a R~16.8 star.
Original predictions (see plot on my page) were made based on the star position and Orcus' ephemeris offset determined in 2009.
Updated predictions based on recent astrometry are accessible on Thomas Widemann's page, see this link
Such an event, if observed at various sites, could allow us to:
- pin down Orcus' radius to km-accuracy, while its diameter is presently poorly constrained between ~ 900 to 1000 km.
- provide its shape, if non-spherical.
- detect a possible faint atmosphere around that body.
- detect its satellite Vanth, or other small satellites.