10th Planet has a Moon - Universe Today
The newly discovered 10th planet - which the discoverers have dubbed "Xena" - appears to have a moon of its own. Nicknamed "Gabrielle", this moon is 100 times fainter than Xena, and seems to orbit the planet once every couple of weeks. It's estimated to be 1/10th the size of Xena, so approximately 250 km (155 miles) across. The powerful Hubble Space Telescope will be turning its gaze on the pair in November/December, and should reveal even more details.