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Hubble telescope spots fifth moon orbiting Pluto (+video)

Almost exactly a year after it spotted a fourth moon orbiting the icy dwarf planet, the Hubble Space Telescope has detected a fifth one.

By Mike WallSPACE.com / July 11, 2012

This image, taken by NASA's Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5, as photographed by Hubble's Wide Field Camera 3 on July 7, 2012.

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

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A tiny new moon has been discovered orbiting Pluto, scientists announced today (July 11).

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Astronomers have discovered an irregular shaped moon, between 6 and 15 miles across, circling the infamous dwarf planet on an orbit 59,000 miles in diameter.

Researchers using NASA's Hubble Space Telescope found the moon, bringing the number of known Pluto satellites to five. The discovery comes almost exactly one year after Hubble spotted Pluto's fourth moon, a tiny body currently called P4.

"Just announced: Pluto has some company -- We've discovered a 5th moon using the Hubble Space Telescope!" Alan Stern, of the Southwest Research Institute in Boulder, Colo., announced via the Twitter social networking website today.

Stern is principal investigator of NASA's New Horizons spacecraft, which is scheduled to fly by the Pluto system in 2015. It will be the first mission ever to visit the dwarf planet.

Pluto's other moons are Charon, Nix, Hydra and P4. Charon is by far the largest, measuring 648 miles (1,043 kilometers) across. Nix and Hydra range between 20 and 70 miles (32 to 113 km) wide, while P4 is thought to be 8 to 21 miles (13 to 34 km) across. 

The new moon looks a lot more like P4 than like Charon.

"It's smaller than P4," Stern told SPACE.com.

"We're finding more and more, so our concern about hazards is going up," he added, referring to the collision risk New Horizons will face when it cruises by Pluto in a few years. [The Moons of Pluto Revealed (Photos)]

The new Pluto moon has been provisionally named S/2012 (134340) 1, though it's also going by the moniker P5. It was discovered using the Wide Field Camera 3 on the Hubble Space Telescope during a series of observations in late June and early July.

P5 appears to be irregularly shaped, with a diameter between 6 and 15 miles (10 to 24 km). It zips around Pluto at an average distance of 29,000 miles (47,000 km), in an orbit thought to be coplanar with the dwarf planet's other satellites, researchers said.

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