|
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, 29, and July 7 and 9.
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.
Source: NASA Goddard Space Flight Center
