SETI Institute Astronomer Mark Showalter Discovers a Fifth Moon Orbiting Pluto

A team of astronomers led by SETI Institute Astronomer Mark Showalter using NASA's Hubble Space Telescope is reporting the discovery of another moon orbiting the icy dwarf planet 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 moons form a series of neatly nested orbits, a bit like Russian dolls," said team lead
Mark Showalter of the SETI Institute in Mountain View, Calif.

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.

The team is using Hubble's powerful vision to scour the Pluto system to uncover potential
hazards to the New Horizons spacecraft. Moving past the dwarf planet at a speed of
30,000 miles per hour, New Horizons could be destroyed in a collision with even a
BB-shot-size piece of orbital debris.

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

"The inventory of the Pluto system we're taking now with Hubble will help the New Horizons
team design a safer trajectory for the spacecraft," added Alan Stern of the Southwest
Research Institute in Boulder, Colo., the mission's principal investigator.

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.

Provisionally designated S/2012 (134340) 1, the latest moon was detected in nine separate
sets of images taken by Hubble's Wide Field Camera 3 on June 26, 27, and 29, 2012 and July 7 and 9, 2012.

In the years following the New Horizons Pluto flyby, astronomers plan to use the infrared vision of Hubble's planned successor, NASA's James Webb Space Telescope, for follow-up observations. The Webb telescope will be able to measure the surface chemistry of Pluto, its moons, and many other bodies that lie in the distant Kuiper Belt along with Pluto.

The Pluto team members are M. Showalter (SETI Institute), H.A. Weaver (Applied Physics Laboratory, Johns Hopkins University), and S.A. Stern, A.J. Steffl, and M.W. Buie
(Southwest Research Institute).

For images and more information about the Pluto system and the Hubble telescope, visit:

http://hubblesite.org/news/2012/32

http://www.nasa.gov/hubble

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.