Hubble Discovers Fifth Moon Orbiting Pluto

Posted on July 11, 2012

Fifth Moon Found Orbiting Pluto


Astronomers using NASA's Hubble Space Telescope have discovered another moon orbiting Pluto. The moon (P5) 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. The discovery increases the number of known moons orbiting Pluto to five.

Team lead Mark Showalter of the SETI Institute says, "The moons form a series of neatly nested orbits, a bit like Russian dolls."

Pluto's largest moon, Charon, was discovered in 1978 in observations made at the United States Naval Observatory in Washington, D.C. Hubble observations in 2006 uncovered two additional small moons, Nix and Hydra. In 2011 another moon, P4, was found in Hubble data.

Harold Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., says, "The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system."

The astronomers are using data from Hubble to uncover potential hazards to the New Horizons spacecraft. New Horizons will be moving past dwarf planet Pluto at a speed of 30,000 miles per hour in 2015. The astronomers say it could be destroyed in a collision with even a BB-shot-size piece of orbital debris.

Photo: NASA, ESA, and M. Showalter (SETI Institute)