Pluto's fifth moon: five fascinating facts

Using data from the Hubble telescope, SETI scientists spotted a fifth moon orbiting the icy dwarf planet Pluto.

|
NASA/ESA/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 Saturday.

Scientists announced the discovery of a new moon around Pluto today (July 11), bringing the dwarf planet's number of known satellites to five.

The newfound Pluto moon was spotted by researchers using NASA's Hubble Space Telescope. The instrument has also found three other Pluto satellites — P4 last year, and Nix and Hydra in 2005. (The dwarf planet's other known moon, Charon, was discovered in 1978 at the United States Naval Observatory Flagstaff Station in Arizona.)

Here are a few fun facts about the new moon:

Its name is a mouthful

The fifth Pluto moon has been provisionally named S/2012 (134340) 1, but it's unlikely anyone other than astronomers will ever call it that. The satellite also currently goes by the less clunky moniker P5, though that won't last forever.

The International Astronomical Union oversees the naming of celestial bodies, and its guidelines stipulate that objects in Pluto's neighborhood receive mythological names associated with the underworld. Pluto, Charon, Nix and Hydra already meet this requirement; P4 and P5 will someday, too. 

It's a tiny satellite

P5 is nothing like our own moon, a giant orb massive enough to be rounded into a sphere by its own gravity. Rather, researchers think P5 is irregularly shaped, with a diameter between 6 and 15 miles (10 to 24 kilometers).

P5 is thus likely the smallest of Pluto's known satellites. Charon measures 648 miles (1,043 km) across, Nix and Hydra range between 20 and 70 miles (32 to 113 km) wide, and P4 is thought to be 8 to 21 miles (13 to 34 km) across. [The Moons of Pluto Revealed (Photos)]

For comparison, Earth's moon is roughly 2,150 miles (3,460 km) wide.

It's not too far from Pluto

P5 zips around Pluto at an average distance of 29,000 miles (47,000 km), placing it outside the orbit of Charon but inside the orbits of Nix, Hydra and P4. The orbits of all five known Pluto moons are roughly coplanar, researchers said.

Earth's moon, on the other hand, circles our planet from about 239,000 miles (385,000 km) away.

P5 makes spacecraft operators nervous

P5's discovery is exciting for researchers who study the outer solar system, but it's likely causing some of them a bit of anxiety as well.

NASA's New Horizons spacecraft is headed to Pluto for a 2015 flyby of the dwarf planet. The detection of P5, and P4 last year, show that the Pluto system is more crowded than scientists had thought. So New Horizons may have to watch its step, since a collision with a particle as small as a BB could take the fast-moving spacecraft out.

"We're finding more and more, so our concern about hazards is going up," New Horizons principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colo., told SPACE.com.

Stern and others are pointing Hubble at the Pluto system to get a better handle on those hazards, and the inventory they produce should help minimize New Horizons' risks, researchers said.

It may be shrapnel from a huge collision

At roughly 1,430 miles (2,300 km) across, Pluto is considerably smaller than Earth's moon. So researchers are intrigued by its complex collection of satellites.

Scientists currently think that all five of Pluto's known moons are relics of a massive collision between the dwarf planet and another large object in the Kuiper Belt — the ring of icy bodies beyond Neptune's orbit — long ago.

Follow SPACE.com senior writer Mike Wall on Twitter@michaeldwall or 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.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

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.

QR Code to Pluto's fifth moon: five fascinating facts
Read this article in
https://www.csmonitor.com/Science/2012/0713/Pluto-s-fifth-moon-five-fascinating-facts
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe