Fourth Moon Discovered in the Pluto System

Fourth Moon Discovered in the Pluto System

The hue and cry over demoting Pluto from the status of a planet to a “dwarf planet” has not subsided, but today NASA announced that “the Pluto system” is growing. Based on observations from the Hubble Space Telescope, a fourth moon has been discovered.

Pluto’s first moon, Charon, was identified in 1978 by the U.S. Naval Observatory. Using the Hubble Space Telescope, astronomers now have found three more: Nix and Hydra in 2005, and this new one that is temporarily designated P4.

P4 is very small, with a diameter of just 8-21 miles. Charon is 648 miles is diameter, while Nix and Hydra are in the range of 20-70 miles.

NASA’s New Horizons spacecraft will reach the Pluto system in 2015 to provide more detailed data about the dwarf planet and its moons. NASA quoted New Horizons principal investigator Alan Stern as calling the new finding “a fantastic discovery.”

The International Astronomical Union created the term “dwarf planet” in 2006 and moved Pluto and the asteroids Eris and Ceres into that class of objects.

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