NASA: Hubble discovers a fifth moon orbiting Pluto

Posted at 8:17 AM, Jul 12, 2012
and last updated 2012-07-12 08:17:01-04

BALTIMORE, Md. (SPACE TELESCOPE SCIENCE INSTITUTE) - A team of astronomers 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).

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 conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.


About the Object
Object Name: P5, S/2012 (134340) 1
Object Description: Fifth Discovered Moon of Pluto
Distance: Although its orbit is highly eccentric, Pluto's average distance from the Sun is 39.44 astronomical units (roughly 3.6 billion miles or 5.9 billion kilometers). P5's distance from Pluto is 26,000 miles or 42,000 kilometers.
Dimensions: Pluto has a diameter of roughly 1,416 miles (2,280 kilometers) at the equator.
About the Data
Data Description: This image was created from HST data from proposal 12801: H. Weaver (APL/JHU), M. Showalter (SETI Institute), S.A. Stern, M. Buie, W. Merline, and A. Steffl (Southwest Research Institute), H. Throop (Planetary Science Institute), and R. Soummer and M. Mutchler (STScI)
Instrument: WFC3/UVIS
Exposure Date(s): June 26, 27, 29, 2012 and July 7 and 9, 2012
Filters: F350LP (Long Pass)
About the Release
Credit: NASA, ESA, and M. Showalter (SETI Institute)
Release Date: July 11, 2012
Color: This image was originally black and white and recorded only overall brightness. These brightness values were translated into a range of bluish hues. Such color "maps" can be useful in helping to distinguish subtly-varying brightness in an image. The colors in this image are not what human eyes would see looking at Pluto.

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