Artist's concept of Kuiper Belt Object 2003 UB313 (non-annotated)

This is an artist's concept of Kuiper Belt object 2003 UB313 (nicknamed Xena) and its satellite Gabrielle.

Ground-based observations suggested that Xena was about 30 percent greater in diameter than Pluto, but Hubble's Advanced Camera for Surveys images, taken on Dec. 9 and 10, 2005, yielded a diameter of 1,490 miles with an uncertainty of 60 miles (about 2400 kilometres with an uncertainty of 100 kilometres) for Xena. Pluto's diameter, as measured by Hubble, is 1,422 miles.