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Thursday, July 21, 2011

New but tiny moon found orbiting Pluto

Pluto may not have full planet status but the distant, icy rock at the fringe of the solar system has three more moons than Earth. The tiny new moon — announced July 20 and called P4 for now — brings the number of known Pluto satellites to four.

And the find, made with the Hubble Space Telescope, suggests that NASA's New Horizons probe could make some big discoveries, too, when it makes a close flyby of Pluto in 2015, researchers said.

Pluto's largest moon, Charon, is 648 miles (1,043 km) across. The other two, Nix and Hydra, are between 20 and 70 miles in diameter (32 to 113 km), NASA said.

P4 is located between the orbits of Nix and Hydra, both of which were discovered by Hubble in 2005. Charon was discovered in 1978 at the U.S. Naval Observatory.

All four of Pluto's moons are believed to have formed when Pluto and another planet-sized body collided in the early history of our solar system. Earth's Moon may have formed the same way.

P4 was first seen in a photo taken by Hubble on June 28 and was confirmed in subsequent Hubble pictures taken July 3 and July 18, NASA said.

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