Hubble telescope spots fifth moon orbiting Pluto

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

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

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

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.

"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., in a statement announcing the new moon.

Charon was first spotted in 1978, 48 years after the discovery of Pluto. Nix and Hydra were found by Hubble in 2005.

Pluto orbits 3.65 billion miles (5.87 billion km) from the sun on average, about 39 times farther away than Earth does. For more than 75 years after its discovery, the object was regarded as a full-fledged planet, but things changed in 2006.

That year, the International Astronomical Union reclassified Pluto a dwarf planet, since it shares orbital space with lots of other objects out in the Kuiper Belt, the ring of icy bodies beyond Neptune.

With another moon to account for around Pluto, NASA's New Horizons mission team is now taking a fresh look at the spacecraft's planned flyby in 2015 to make sure it will zip by the dwarf planet safely while observing the complex planetary system.

"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 New Horizons team member 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," Stern added in a statement.

This story was updated at 11:51 a.m. ET with new details and comments.

Follow SPACE.com senior writer Mike Wall on Twitter @michaeldwallor SPACE.com @Spacedotcom. We're also onFacebook and Google+.

Copyright 2012 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.