There are three moons! (Pluto)

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-10-31 01:31pm

Space.com wrote: Two More Moons Discovered Orbiting Pluto
By Robert Roy Britt
Senior Science Writer
posted: 31 October 2005
01:01 pm ET

Two small moons have been discovered orbiting Pluto, bringing the planet's retinue of known satellites to three and leaving scientist to wonder how it could be.

The newfound moons orbit about 27,000 miles (44,000 kilometers) from Pluto, more than twice as far as Charon, Pluto's other satellite. They are 5,000 times dimmer than Charon.

Preliminary observations suggest they are in circular orbits around Pluto and in the same plane as Charon, said Hal Weaver of the Johns Hopkins Applied Physics Laboratory.

"That suggests they probably formed at the same time as Charon," Weaver told SPACE.com in a telephone interview Friday. NASA planned a teleconference with reporters Monday at 1 p.m. ET to announce the discovery.

While scientists had predicted there might be more moons, the newfound setup is surprising nonetheless, in part because Pluto is smaller than our own Moon.

"It's almost like a mini solar system," Weaver said. "How can something about 70 percent the size of Earth's Moon have all these satellites? How can that happen? We're going to have to explain that."

The leading theory for the formation of Charon involves a large object striking Pluto. The debris from that collision could have formed the two smaller moons, Weaver speculates. It can't be ruled out that they might have been captured into the system, but that seems very unlikely, he said.

The two new moons are between 30 and 100 miles (45 to 160 kilometers) in diameter, Weaver said. There is not enough data to pin their size down exactly, however. Pluto is 1,430 miles wide and Charon's diameter is about 730 miles.

The moons were found using the Hubble Space Telescope.

Piece of the puzzle

The discovery represents one more piece of an increasingly complex puzzle in the outer solar system, a place that astronomers look to for clues in understanding how it all formed 4.5 billion years ago in the wake of the Sun's birth.

Lately, so many objects have been found in so many configurations out there, that astronomers can't even agree on what to call them.

Though popularly considered a planet, Pluto is now viewed by most astronomers to be a member of the Kuiper Belt, a vast sea of frozen worlds beyond Neptune that hadn't been discovered when Pluto was found 75 years ago. The region includes other round objectswith moons, and one recently discovered world is larger than Pluto.

For now, Pluto is the only Kuiper Belt object known to have more than one companion.

"Our result suggests that other bodies in the Kuiper Belt may have more than one moon as well," said team co-leader Alan Stern of the Southwest Research Institute in Boulder, Colo.

Stern heads up the New Horizons mission to Pluto and the Kuiper Belt, slated for launch early next year. He had long predicted other moons around Pluto.

There could be more moons to find, too, but they would be small.

"These Hubble images represent the most sensitive search yet for objects around Pluto," said team member Andrew Steffl of the Southwest Research Institute, "and it is unlikely that there are any other moons larger than about 10

miles across in the Pluto system."

Easy to find

The moon-hunting project was denied by Hubble planners several times and took years to get approved, and only then after a failed instrument on Hubble last year caused project leaders to add several previously unaccepted observing programs to fill the schedule.

For Hubble, this one was easy.

Unlike many observing projects that require several Hubble orbits – often 15 or more and sometimes many dozens -- Weaver's team needed just two orbits. On the first set of observations they spotted the two points of light, then on the second orbit they found them again and made sure they moved against the background of relatively fixed stars.

The presumed moons are 23rd magnitude, far to dim to be seen with a typical backyard telescope but "relatively easy to see with Hubble," Weaver said.

Then the astronomers dug up old Hubble observations done by colleague Marc Buie of the Lowell Observatory, to see if the same objects had been imaged before.

Weaver said they are pretty sure they've located the moons in the archived photos, and the combination of data is what suggests the moons' circular orbits in the plane of Charon's path.

More Hubble observations are planned for February to confirm the discoveries and pin down the orbits.

The moons are catalogued as S/2005 P1 and S/2005 P2 for now. Once they are confirmed, the discoverers will suggest names, to be approved by the International Astronomical Union.

Source

Post by **Dalton** » 2005-10-31 05:32pm

Wow! That's damn cool.

Kitsune · Post by **Kitsune** » 2005-10-31 07:42pm

Relatively easy for Hubble and basically impossible for any Earth Obseratory....Hmmm

Dark Hellion · Post by **Dark Hellion** » 2005-10-31 08:19pm

Relatively easy for Hubble and basically impossible for any Earth Obseratory....Hmmm

Shhh, once we strip off that pesky atmosphere that causes all the distortion, we won't need hubble anymore. It will save large amounts of money, and free up rockets for more important things, like missions to mars, or putting nukes on the moon to deter terrorists.

CoyoteNature · Post by **CoyoteNature** » 2005-10-31 08:57pm

Wonder how they're that stable, just weird something that small has three moons, one's weird enough.

VT-16 · Post by **VT-16** » 2005-11-01 01:39am

Moons? Bah! I say it's a Mi-Go cluster.... :P

Post by **RogueIce** » 2005-11-01 10:03am

Just out of curiosity, if Charon came to be because something smacked into Pluto and broke off a chunk of it, would it be possible to see where that chunk came from on Pluto, or would it "repair" itself? Or am I failing basic astronomy?

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-11-01 10:48am

RogueIce wrote:Just out of curiosity, if Charon came to be because something smacked into Pluto and broke off a chunk of it, would it be possible to see where that chunk came from on Pluto, or would it "repair" itself? Or am I failing basic astronomy?

Our Moon formed from a Mars-sized object smashing into us and blasting a Moon-sized chunk of mantle into orbit. Do you see an enormous impact basin covering half the planet? No. Such an enormous impact would generally reset any geography the planet had beforehand as the energy transfer would heat it to the point of being rather uniformly molten. So the answer is, it would "repair" itself.

Post by **RogueIce** » 2005-11-01 02:00pm

GrandMasterTerwynn wrote:
RogueIce wrote:Just out of curiosity, if Charon came to be because something smacked into Pluto and broke off a chunk of it, would it be possible to see where that chunk came from on Pluto, or would it "repair" itself? Or am I failing basic astronomy?
Our Moon formed from a Mars-sized object smashing into us and blasting a Moon-sized chunk of mantle into orbit. Do you see an enormous impact basin covering half the planet? No. Such an enormous impact would generally reset any geography the planet had beforehand as the energy transfer would heat it to the point of being rather uniformly molten. So the answer is, it would "repair" itself.

Ah, thanks.

Still, it would be kinda cool to see a planet with a chunk missing, no matter how unrealistic it would be.

Grandmaster Jogurt · Post by **Grandmaster Jogurt** » 2005-11-01 03:17pm

RogueIce wrote:[snip]

Ah, thanks.

Still, it would be kinda cool to see a planet with a chunk missing, no matter how unrealistic it would be.

If it makes you feel better, there're two moons (Tethys and Mimas) that have a crater with a diameter a significant fraction of their own, and one (Hyperion) which looks to be a chunk of a destroyed body.

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-11-01 03:20pm

RogueIce wrote:
GrandMasterTerwynn wrote:
RogueIce wrote:Just out of curiosity, if Charon came to be because something smacked into Pluto and broke off a chunk of it, would it be possible to see where that chunk came from on Pluto, or would it "repair" itself? Or am I failing basic astronomy?
Our Moon formed from a Mars-sized object smashing into us and blasting a Moon-sized chunk of mantle into orbit. Do you see an enormous impact basin covering half the planet? No. Such an enormous impact would generally reset any geography the planet had beforehand as the energy transfer would heat it to the point of being rather uniformly molten. So the answer is, it would "repair" itself.
Ah, thanks.

Still, it would be kinda cool to see a planet with a chunk missing, no matter how unrealistic it would be. :)

If you look at Saturn's moon, Mimas, you can come close. On it is an impact crater which is a third of the moon's diameter. This is about the closest one can get to blasting a large hole in a world without resetting all it's geography in a molten orgy of destruction.

Elheru Aran · Post by **Elheru Aran** » 2005-11-01 03:55pm

Ah, yes, the infamous 'Death Star' moon...

Dark Hellion · Post by **Dark Hellion** » 2005-11-01 04:13pm

Shhh, there is no secret "Death Star" on Mimas. None at all. I mean, no one would be installing a large laser of doom designed to hold the world hostage and impress woman, no one at all.
Oop, gotta go.

wilfulton · Post by **wilfulton** » 2005-11-01 10:20pm

Dark Hellion wrote:Shhh, there is no secret "Death Star" on Mimas. None at all. I mean, no one would be installing a large laser of doom designed to hold the world hostage and impress woman, no one at all.
Oop, gotta go.

Hmpf, how's that for a pickup line? Hey baby, like my...superlaser? Hooo...down boy!"

In the meantime, I absolutely can't wait for the new horizons spacecraft to get there and start sending back pictures! Pity it won't get there until 2015. Damn it all. We need to start developing better engines than these piss ant chemical rockets that send you nowhere fast!