The tenth planet discovered recently is nicknamed as “Xena”. The Hubble Telescope found that the new planet is just little larger than Pluto.
Image Source: jpl.nasa.gov/spaceimages/images/largesize/PIA17801_hires.jpg
Hubble observation taken on December 9, 2005 indicate that the tenth planet has a diameter of 1,4900 miles while Pluto, measured by Hubble, is 1,422 miles.