2003 UB313 tenth planet". Artwork of the tenth planet 2003 UB313, and its moon. 2003 UB313 is a temporary name, as are the unofficial names: Xena (planet) and Gabrielle (moon). Official names are being decided by the International Astronomical Union. The planet is thought to be around 3000 kilometres across, which is far larger than Pluto. It takes 560 years to orbit the Sun. 2003 UB313 is the largest known member of the Kuiper Belt of rocky, icy bodies, including Pluto, that orbit the Sun beyond Neptune. The discovery was made from observations made in 2003 at the Palomar Observatory, USA, by Mike Brown, Chad Trujillo and David Rabinowitz, and announced in July 2005. The moon was observed in September 2005. The Milky Way is the bright band of stars in the background at right."