From NASA in the USA:
Hubble Discovers a Fifth Moon Orbiting Pluto
The moon is estimated to be irregular in shape and 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system.
The discovery increases the number of known moons orbiting Pluto to five.
The Pluto team is intrigued that such a small planet can have such a complex collection of satellites. The new discovery provides additional clues for unraveling how the Pluto system formed and evolved. The favored theory is that all the moons are relics of a collision between Pluto and another large Kuiper belt object billions of years ago.
The new detection will help scientists navigate NASA’s New Horizons spacecraft through the Pluto system in 2015, when it makes an historic and long-awaited high-speed flyby of the distant world.
See also here.
Pluto’s P4 moon was discovered in July 2011. Also by the Hubble telescope.
It is good that the plans of the George W Bush administration in the USA to kill the Hubble telescope did not go ahead.
And the first full color photo of Pluto.