Volume: 04, Issue: 05 11/02/2005 
Artist concept showing the Pluto system from the surface of one of the candidate moons. Image courtesy NASA/ESA/G. Bacon (STScI).
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In the short-exposure image, the candidate moons cannot be seen; they do appear in the middle and right-hand images with longer exposure times. Image courtesy NASA/ESA/H. Weaver (JHU/APL)/A. Stern (SwRI)/Hubble Space Telescope Pluto Companion Search Team.
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Other Articles in This Issue:
Cassini Uncovers More Saturn Mysteries
International Space Station Celebrates Milestone
Spitzer Catches Black Widow Nebula
Chat about Spaceflight with a Former Astronaut

Hubble Reveals Possible New Moons Around Pluto

Pluto’s moon Charon may have siblings: astronomers have discovered two more possible moons orbiting the tiny planet. NASA’s Hubble Space Telescope uncovered evidence of the new moons, which astronomers are working to verify.

If confirmed, the new moons could offer insights into the nature and evolution of the Pluto system; Kuiper Belt Objects with satellite systems; and the early Kuiper Belt. The Kuiper Belt is a vast region of icy, rocky bodies beyond Neptune’s orbit.

"If, as our new Hubble images indicate, Pluto has not one, but two or three moons, it will become the first body in the Kuiper Belt known to have more than one satellite," said Hal Weaver of the Johns Hopkins Applied Physics Laboratory. He is co-leader of the team that made the discovery.

Pluto was discovered in 1930. Charon, Pluto’s only confirmed moon, was discovered by ground-based observers in 1978. The planet resides about 3 billion miles from the sun in the heart of the Kuiper Belt.

"Our result suggests other bodies in the Kuiper Belt may have more than one moon. It also means planetary scientists will have to take these new moons into account when modeling the formation of the Pluto system," said Alan Stern of the Southwest Research Institute, co-leader of the research team.

The candidate moons, provisionally designated S/2005 P1 and S/2005 P2, were observed approximately 27,000 miles away from Pluto. The objects are roughly two to three times as far from Pluto as Charon.

The team plans to make follow-up Hubble observations in February to confirm the newly discovered objects are truly Pluto's moons. Only after confirmation will the International Astronomical Union consider names for S/2005 P1 and S/2005 P2.

The Hubble's Advanced Camera for Surveys observed the two new candidate moons on May 15, 2005. The candidates are roughly 5,000 times fainter than Pluto. Three days later, Hubble looked at Pluto again. The two objects were still there and appeared to be moving in orbit around Pluto.

Images and more information are available on the Web: http://www.nasa.gov/vision/universe/solarsystem/hubble_pluto.html

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