Pluto may not be a planet, but it certainly has quite a family of satellites! On top of the three already known (Charon, Nix and Hydra), astronomers studying the Pluto with the Hubble Space Telescope have now found a fourth moon. It hasn’t yet been officially named, so it carries the temporary label of ‘P4’. What’s remarkable is that it could be seen at all – current estimates are that it is somewhere between only 13 and 34km across. That is a vanishingly small thing to see from over 4.5 billion kilometers away!
For more details, read the official release here: http://hubblesite.org/news/2011/23