Charon, largest moon of Pluto - Windows to the Universe Charon - Pluto's biggest moon Charon is a moon of Pluto. Pluto has moons . Charon is much larger than Pluto's other moons. James Christy discovered Charon on June 22, 1978. Charon is nearly as big as Pluto. Some astronomers call Pluto and Charon a " double planet ". Charon is also very close to Pluto. Because Charon is so close, it goes around Pluto fast. It only takes Charon a little more than six days to orbit Pluto. Did you know that we can only see one side of our Moon from Earth ? That's because the Moon spins around in exactly the same amount of time it takes it to orbit Earth. The same thing is true for Charon and Pluto. Someone on Pluto could only ever see one side of Charon. Now here's the really strange part. Pluto also spins exactly as fast as Charon. So on one side of Pluto, Charon is always up in the sky. A person on the other side of Pluto would never see Charon at all! Charon is made of rock and ice , like Pluto.

Some astronomers think Charon formed when a large object crashed into Pluto. That is a lot like how scientists think Earth's moon formed . Other scientists aren't quite so sure that Charon was formed that way. Charon is named after a character from Greek mythology . Charon was the ferryman of the dead. He took people who had just died across a river in a boat. He took them to Hades, the underworld. Hades was also the name of the god of the underworld. In Roman mythology, Hades was called Pluto . Last modified January 23, 2006 by Randy Russell . Shop Windows to the Universe Science Store! Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game ! Windows to the Universe Community News Fly Over Charon, Pluto’s Biggest Moon | WIRED Time of Publication: 6:44 pm. 6:44 pm Fly Over Charon, Pluto’s Biggest Moon Like Pluto, Charon is not a planet. But who needs recognition from the stuffy, earthbound International Astronomical Union? Especially when you’ve got ice volcanoes?

That’s right, ice volcanoes . See, Charon’s two hemispheres are so different that scientists’ best guess for why one is so much smoother is that ice erupts from below the dwarf moon’s surface. Bordering the the slick lowlands is a massive canyon system, which you can see in the video above. The flight begins high above Mordor, which is what Charon-ologists have named the dark spot in the moon’s polar highlands. New Horizons’ atmospheric scientists believe that Mordor might actually be nitrogen deposits captured from Pluto (which is constantly shedding the stuff). Then the flight swoops into the canyons, a system that seems to extend at least 1,000 miles. The canyons might even completely encircle Charon—sort of like the hug the moon deserves from those meanies at the IAU. Author: Nick Stockton. Nick Stockton Science Date of Publication: 07.01.16. Time of Publication: 6:09 pm. 6:09 pm NASA Confirms New Horizons Is Hurtling Towards Some Barren Space Rock Named 2014 MU69 The New Horizons probe.

NASA Remember how excited you were last summer? No, not because you found a booth at the state fair selling deep fried beer . I’m talking about New Horizons , sillies. Well get ready for another bout of excitement, because NASA has greenlit New Horizons’ next target: a lump of rock out in the Kuiper Belt called 2014 MU69 . And don’t worry if you’re still exhausted from last year’s Pluto-brations (or the Juno mission’s orbital insertion happening this July 4th). New Horizons isn’t scheduled to rendezvous with 2014 MH69 until January 1st, 2019, so you have plenty of time to get ready. Because what better way is there to spend your New Years’ hangover than sitting in the dark and waiting for a space probe five and a half billion miles away to send a few squawks home confirming that it passed its target successfully? But wait, you ask. Doesn’t this 2014 MU69 character sound familiar? It should.

Nineties kids will remember that in season three of Big Bad Beetleborgs, a cyborg monster called 2014 MU69 kidnaps Flabber, leading Drew, Jo, and Roland on a wild chase through the Hillhurst suburbs. Just kidding, everyone knows that show only had two seasons. 2014 MU69 should really only sound familiar to Pluto-heads who were paying attention last August when NASA first announced the Kuiper Belt object as New Horizons’ next target. So what is new? Well, this is NASA just doubling down, saying it has allotted funding to the mission. Yay, money! Time of Publication: 6:33 pm. 6:33 pm Pluto May Have Ice Volcanoes, and New Horizons Got a Peek Two of Pluto’s mountains, Wright Mons and Piccard Mons, could actually be ice volcanoes. The blue points in the middle of each circle indicate a dip in elevation. NASA/JHUAPL/SWRI Today, the New Horizons team dropped some science from an unfamiliar location. I mean, yes, all its results are coming from the Pluto system, but today Alan Stern & Co.

presented this mountainous map at the annual meeting of the American Astronomical Society’s Division of Planetary Sciences. And it looks…kind of familiar. The blue spot in the middle of the informally-named Piccard Mons and that belly button-looking depression in neighboring Wright Mons are areas of low elevation. And on Earth, that kind of hole in the middle of a mountain only means one thing: volcano. OK, we get it. New Horizons was a complicated mission. One does not simply walk onto Pluto, right? Ooh! Wait! I got it. Ring of mountains? Volcano in the middle? It’s Mordor! Now, sure, these volcanoes are really only maybe-volcanoes, because Pluto is, like, really far away, man. And so it’s hard to tell exactly what’s going on. If they are volcanoes, they won’t be spewing magma or lava bombs. These would be cryovolcanoes. Ice vulcanism! The New Horizons team thinks that these structures could have formed when a slurry of water ice, nitrogen, ammonia, or methane erupted from beneath the dwarf planet’s surface.

The One Ring wouldn’t dissolve into steaming fizz; it’d freeze and crackle into shards. Which would be cool. Whatever works, right? As for this video of Pluto’s wobbling, bobbling, precessing moons? Yyyyyeah. Pluto’s moons have super-weird shapes, which might be why they orbit like drunk college kids circling that one bar that doesn’t card. Or it could be that Charon, the biggest moon, exerts extra pull on all the smaller ones. Either way, don’t stare too long. Charon’s Organa Crater Glows With the Force … Er, Ammonia NASA/JHUAPL/SwRI Not so long ago, on the far away moon of Charon, a tiny space probe spied a strange energy signature emanating from a crater named after Luke Skywalker’s sister. No, it wasn’t midi-chlorians. Organa crater, named for Star Wars heroine Princess Leia, is actually coated with ammonia, though scientists are still baffled as to why. Ammonia is pretty abundant in the galaxy. Because it stays liquid at very low temperatures, many scientists believe it is behind a lot of the geologic activity on icy worlds like Charon.

In fact, based on telescope observations from Earth and photographic evidence of geomorphology taken from New Horizons, scientists expected the faraway moon to be covered with the stuff. “But we haven’t seen it everywhere. This crater is an exception,” says Will Grundy, astronomer at Lowell Observatory in Arizona and ice expert for the New Horizons mission. The source of the ammonia is a mystery, but Lowell and his co-investigators shared a few hypotheses. “One speculation is that this is just a more youthful crater than the rest,” says Grundy. In this scenario, ammonia would be everywhere under the top layer of Charon’s surface. Organa could be so young that space radiation hasn’t yet destroyed the underlying ammonia exposed by the initial meteor strike. “But we really don’t know the timescale at which that happens,” says Grundy. Another idea is perhaps the meteor that created Organa crater was ammonia-rich, and left some of the stuff behind. The final speculation is that Organa is roughly the same age as other Charonian craters, but happens to be located over an unusually rich subsurface smear of ammonia. “But these are all pretty speculative, and I’m not sure if it’s useful to weigh one over another,” says Grundy.

Grundy says with better imagery the New Horizons team could probably tease out some clues from the geomorphology surrounding the crater, but that’s not likely to happen. New Horizons was three times as far from Charon as Pluto during the flyby. “We’re never going to get as high a resolution as we have with Pluto,” says Grundy. Organa’s ammonia signature is even more striking compared to a nearly identical crater to the south, called Skywalker. As of press time, there was no indication that the sibling craters had ever accidentally kissed . NASA/JHUAPL/SwRI Time of Publication: 5:25 pm. 5:25 pm Watch: Pluto’s Sunset as Seen by New Horizons It’s only been two months since New Horizons whizzed past Pluto, some 4.7 billion miles from Earth. Now, the space probe is in the process of sending back tens of gigabits of data collected during the flyby, including increasingly kick-ass photos of the icy rock’s surface. The most recent images released by NASA show the dwarf planet backlit by the sun, revealing mountain ridges and atmospheric haze—lots and lots of haze.

They also offer a more detailed look at Sputnik Planum, the smooth, icy expanse that looks like a big heart. Enjoy, and keep coming back for more photos—they’ll keep coming in over the next year. Time of Publication: 1:26 pm. 1:26 pm New Photos of Pluto’s Haze, Backlit and In Glorious Detail Slide: 1 / of 6. Caption: Caption: Just after it whizzed past Pluto, New Horizons took this photo of the dwarf planet backlit by the sun. The image shows mountain ridges and atmospheric haze—lots and lots of layers of atmospheric haze.NASA/JHUAPL/SWRI Slide: 2 / of 6. Caption: Caption: Icy mountains (left) contrast with the smooth expanse of Sputnik Planum (right), probably covered in nitrogen ice.NASA/JHUAPL/SWRI Slide: 3 / of 6. Caption: Caption: Sunset on Pluto! The sun shines through the “fog” near Pluto’s surface. The shadows come from hills and mountains.NASA/JHUAPL/SWRI Slide: 4 / of 6.

Caption: Caption: This is the heart-shaped bright spot on Pluto, also known as Sputnik Planum. The white color likely comes from nitrogen ice.NASA/JHUAPL/SWRI Slide: 5 / of 6. Caption: Caption: Red arrows show where a glacier flows into Sputnik Planum. Blue arrows point to the edge of the glacier.NASA/JHUAPL/SWRI Slide: 6 / of 6. Caption: Caption: Another view of the glaciers, showing more detail.NASA/JHUAPL/SWRI Advertisement Time of Publication: 6:38 pm. 6:38 pm The First Pluto Photos From New Horizons’ Massive Data Dump Slide: 1 / of 7. Caption: Caption: This patched-together image of Pluto shows New Horizons' views of the dark, cratered Cthulhu Regio below Sputnik Planum's bright, left lobe. NASA/JHUAPL/SWRI Slide: 2 / of 7.

Caption: Caption: A large region of jumbled, broken terrain on the northwestern edge of Sputnik Planum (that's the big heart).NASA/JHUAPL/SWRI Slide: 3 / of 7. Caption: Caption: Scientists are still working out what causes these enigmatic fields of dark, aligned ridges. If they are dunes, that could mean Pluto has wind. NASA/JHUAPL/SWRI Slide: 4 / of 7. Caption: Caption: More detail of Pluto's big heart-shaped ice plain, Sputnik Planum.NASA/JHUAPL/SWRI Slide: 5 / of 7. Caption: Caption: Two different versions of an image of Pluto's haze layers, taken by New Horizons as it looked back at Pluto's dark side.NASA/JHUAPL/SWRI Slide: 6 / of 7. Caption: Caption: Pluto's bright, high-altitude atmospheric haze produces a twilight that softly illuminates the surface before sunrise and after sunset.NASA/JHUAPL/SWRI Advertisement Slide: 7 / of 7.

Caption: Caption: Charon's surface indicates a surprisingly complex geological history, including tectonic fracturing and mountainous uplift.NASA/JHUAPL/SWRI Related Galleries Something Deep Inside Pluto Is Replenishing Its Atmosphere NASA/JHUAPL/SwRI Pluto has a problem: Its thin, nitrogen atmosphere shouldn’t be there. Ultraviolet rays from the sun should have knocked it away, molecule by molecule, in the dwarf planet’s first few thousand years. Four billion years later, Pluto’s atmosphere is still there, a gauzy interplanetary mystery. Okay, it’s really scientists who have the problem, because it’s not like there are nitrogen-breathing Plutonians down there pacing worriedly over impending suffocation. Right, NASA? Right?!? No, all worrying has been purely academic, expressed in papers like the one published earlier this month by a pair of New Horizons scientists who examined the trio of prevailing theories behind the atmosphere’s perplexing replenishment. High noon on Pluto looks like dusk on Earth. But even that small amount of solar energy is enough to turn frozen nitrogen on Pluto’s surface into gas.

Once aloft, Pluto’s gravity is too weak to keep the particles from being blown away by ultraviolet radiation. (In case you’re wondering, Earth’s mass is enough to keep its atmosphere mostly safe from getting blown off into space.) Pluto has been around for about four billion years, and according to the best math, it should have lost about 7,000,000,000,000,000,000,000 grams of nitrogen (give or take a zero) since then. But scientists currently estimate that the planet has about 30,000,000,000,000,000 grams of nitrogen atmosphere, and loses about 1,500,000,000,000 grams each year. “Basically, it would take only a few thousand to tens of thousands of years to lose that atmosphere,” says Kelsi Singer, post-doctoral researcher at the Southwest Research Center and co-author of the paper. Basically, that’s not a very long time.

Considering that Pluto has been around for more than four billion years, the odds are pretty friggin’ slim that humans would meet the dwarf planet during its brief phase of atmosphere-having. No, something is replenishing the supply. Scientists, you got some ‘splaining to do. There are two basic mechanisms for resupplying Pluto’s atmosphere: “You can either bring stuff in from the outside or bring stuff up from the inside,” Singer ‘splains. Comets are a handy mechanism for both categories, as they can deposit nitrogen when they impact, or punch holes through the surface to expose quantities of the frozen gas. Singer is an impact expert, so she did the calculations for how much nitrogen a comet would shed, or dig up, upon impact. Her co-author Alan Stern, studies atmospheres ( among other things ) and ran the numbers for gas loss. But even with their most conservative estimates—the maximum number of comets, the deepest of impact craters—nothing from off planet could cover the deficit of nitrogen loss. Instead, they offer that the nitrogen is being replenished through more conventional geologic activity like cryovolcanism or tectonic action.

But nobody yet knows what is behind this geologic churning, as Pluto is too small and too old to be holding much remnant energy from its formation. It’s also too far from any planetary body that would be large enough to tidally churn its innards. Something else inside the dwarf planet was causing exhalations. Does a Great Old One stir under the dark equatorial region, ominously nicknamed Cthulhu Reggio? It would explain the Sleeper of R’lyeh’s long absence… Perhaps wisely, Singer and Stern do not explore that chilling hypothesis. The most likely battery for Plutonian heat are huge chunks of uranium or potassium wedged in its rocky core. “Those will emit heat as they break down, and the heat has to go somewhere, so it causes local melting,” says Will Grundy, a planetary scientist, ice expert, and French cheese connoisseur at Lowell Observatory in Arizona. The authors submitted their paper back in May, just as New Horizons was sending home its first images of Pluto. Since then, the probe’s cornucopia of data has supported Singer and Stern’s geologic hypothesis.

“We do seem to be seeing a good deal of recent geologic activity on Pluto, so that’s not a bad sign for our paper,” says Singer. Things will look even better come September and October, when they can make better estimations of the impact rate based on the lossless data showing the dwarf planet’s craters. “We also get data from particle and plasma, that will help us calc the rate of atmospheric escape,” she says. And every bit that arrives will blow away the mystery of Pluto’s missing molecules. The Ices on Pluto’s Surface Are Totally Nuts NASA/JHUAPL/SWRI Earthlings have a sadly unsophisticated view of ice. Terrestrial types mostly think about it in terms of water ice—solid, cold, slick to the touch as it begins to melt in their warm, fleshy hands. But not Plutonians. If you lived on Pluto, you’d have as many names for ice as the Eskimos have for snow: words for carbon monoxide ice, nitrogen ice, and methane ice, all with different properties. Today’s photos back from New Horizons put the spotlight on those frozen solids.

In this top false color image, you can see just how much compositional variety defines Pluto’s surface—from the bright white of the carbon monoxide ice in the middle of Pluto’s “heart,” now officially called Tombaugh Regio, to the bands of colors likely created by the seasonal transport of ices from equator to pole. The blueish spots might be ices that have traveled from the left lobe of Pluto’s heart. And then there’s the ice’s geological activity. “Water ice at Pluto’s temperatures won’t move anywhere,” says New Horizons co-investigator Bill McKinnon. “But these ices are geologically soft and malleable, even at Pluto conditions.” In new high-resolution images from the LORRI camera, scientists can see the flowing solids—including nitrogen ice—in the vast Sputnik Planum interacting with towering mountains, flowing between them and even filling in old impact craters. NASA/JHUAPL/SWRI “We knew there was nitrogen ice on Pluto, but to see evidence for recent geological activity is simply a dream come true,” says McKinnon. Time of Publication: 2:11 pm.

2:11 pm Watch: Fly Over Pluto’s Icy Mountains With New Horizons If the first close-up images of Pluto’s mountain ranges sent home by New Horizons seemed a little underwhelming, it might have been because you couldn’t really get a sense for their scale in a two-dimensional photo. Now NASA has released an amazing simulated video of the space probe’s flyover, helping those features pop out like they should. Those mountain ranges have a name now: Norgay Montes, named after one of the first people to summit Mount Everest, Tenzing Norgay. Some of the peaks seen in this flyover are up to 11,000 feet tall—an impressive stat on its own, but especially so when you consider they’re probably made of ice (the frozen nitrogen and methane that covers most of Pluto’s surface would collapse under themselves at that elevation). The video continues and transports you to the so-called Sputnik Planum, a vast plain of unexpectedly craterless surface that suggests Pluto is geologically quite young (if you can call 100 million years old young).

The plain lies within the region now officially named Tombaugh Regio, after Pluto’s discoverer—but to us, it’ll always be Pluto’s heart . The Many Ices of Pluto’s Surface, in Living Color NASA/JHUAPL/SWRI Today the New Horizons team treated the world to new images of Pluto , Charon , and Hydra , all taken by LORRI, New Horizons’ main imager. But LORRI’s all grey. Still to come are images featuring the full visible light spectrum, plus near infrared from RALPH , the probe’s color and infrared imager. Nothing new from RALPH just yet, but as a tease of what’s to come, New Horizons’ planetary ice expert Will Grundy, of the Lowell Observatory, showed off some methane readings that were sent over in the probe’s final broadcast before it went dark for its July 14 flyby. The bright blue, red, and black pixels—overlaid on a LORRI basemap—represent methane ice accumulations. These colors represent data from just three of RALPH’s 256 infrared wavelengths. As such, they don’t say much more than that Pluto has different types of ice.

“All I’m showing is the diversity of terrains,” says Grundy. But there are some interesting clues. For one, Grundy says that the colors in the ice cap look a lot like the colors in the right side of the giant heart—which today New Horizons informally named the Tombaugh Regio after Pluto’s discoverer, Clyde Tombaugh. “The ices do have distinct properties, different melting points,” Grundy said at an earlier conference, speaking more generally about Pluto’s surface. All vague, all tantalizing, and taken in context with some of the other news revealed today—that Pluto has massive mountains made of water ice and could be geologically active—these slim details hint at big things to come. Pluto may be cold, small, and far away, but the world is anything but dull. Time of Publication: 6:00 pm.

6:00 pm Watch: Everything We Know About Pluto in One GIF Over the course of New Horizons’ nearly decade-long journey to Pluto, mission scientists at NASA, Johns Hopkins, and the Southwest Research Institute have watched the icy rock grow from mere pixels into a real place, with topography and geology and all the things you’d expect from a planet ( even though it technically isn’t one ). Today, after the space probe completed its closest approach to Pluto’s system, the New Horizons team released a new image— the most detailed ever —that shows mountains on the dwarf planet’s southeastern hemisphere. NASA’s Goddard Space Flight Center posted this timeline of Pluto photos , making the accomplishments of the New Horizons team that much more visceral. Take it all in. Charon Comes Into Focus in New Horizons’ Latest Photos NASA/JHUAPL/SWRI Maybe you still haven’t figured out how to say the name of Pluto’s largest moon. Let me help. It’s pronounced “WOW.” I don’t want to interrupt your gasping with too many words, but here are some quick stats on the shot. Draw your eyes to the dark area around the moon’s north pole.

“Informally we’ve been referring to that as Mordor,” says Cathy Olkin, one of the mission’s top planetary scientists, to the delight of everyone. Trace your gaze down the right curve until you reach a notch, at about the 2 o’clock spot. That’s a canyon. A big one, about four to six miles deep. And that’s not all. Move your eyes down and in and follow the huge sash of canyons banding across the planet’s middle. This is about 600 miles across, and according to Olkin could be the result of internal processing. That’s right, active geology. Just as with similar details on Pluto , the team’s speculations about what is causing this geology are so far guarded and vague. But what’s certain is that “something is making these two worlds very, very different,” says Alan Stern, the mission’s principal investigator. Pluto is covered in water ice, Charon has massive cliffs. But the shroud of mystery that covers both is being steadily removed. Everybody, Meet Hydra, Pluto’s Outermost Moon NASA/JHUAPL/SWRI In Greek mythology, the hydra was a many-headed dragon snake with regeneration powers.

That’s impressive, but I’m pretty sure that its namesake moon has officially eclipsed its forbearer. “Pluto and Charon are going to steal the day today, but let’s not forget that Pluto has four small moons as well that we want to collect data on,” says New Horizons project scientist Hal Weaver. “This morning, we got the first really well-resolved images of Hydra.” Prior to this image, the best pictures of Hydra looked like someone took a quick pass of an eraser over a pencil-drawn period. By comparison, each pixel in the relatively crisp little nugget above represents two miles. The cool thing about Hydra is how much we have to learn about it. Before today, Hydra was square. Now we can finally see its shape, a wobbly sort of potato-looking thing. We also know its size: 28 by 19 miles across. “New Horizons makes it easy for us,” says Weaver. “Just count the number of pixels across.” And there’s plenty more to come. As New Horizons floods its team with data, they will learn more about its composition and will develop clues about its origins.

Combined with data from the other four moons and Pluto itself, that data will help scientists pull together an origin story for the tiny planetary system. Time of Publication: 6:12 pm. 6:12 pm What If Pluto Suddenly Disappeared? It is less than three hours until New Horizons’ safe and sound message arrives—or doesn’t. Worrier that I am, I’m still worried that the brave little probe might run afoul of a dastardly space pebble. But there’s something else that’s also been nagging me: What if Pluto suddenly disappeared? It’s a question with long odds—much more improbable than the 1 in 5,000 chance of collision Alan Stern mentioned this morning—and let’s face it, pretty silly. But I still found some experts to scratch my itch. Specifically, I’m curious about the gravitational effects. Would we feel it on Earth? “If Pluto disappeared, it certainly wouldn’t have an effect on Earth,” says Sarah Hörst , a planetary scientist at Johns Hopkins University. Gravity depends on mass, and the force it exerts decreases over distance. Pluto is too tiny, and too far, to affect Earth. And Mars. And Jupiter.

And Saturn, Uranus, and Neptune. Pluto is so tiny compared to everything else that pretty much only its moons would notice if it disappeared. “Notice” meaning they’d shoot off into space. In fact, even New Horizons wouldn’t really be affected. “There’s no magnetometer, and we’re not using any forces around the planet to trigger anything on board,” says Alice Bowman , New Horizons’ mission operations manager. New Horizons’ flyby maneuvers are pre-programmed, so if Pluto suddenly disappeared all it would return are pictures of empty space. And because the light from Pluto would disappear before New Horizons had sent its 4:27pm ET message home, any Earthly telescopes would get the news first. Time of Publication: 5:09 pm. 5:09 pm Really, Here’s How You Pronounce “Charon”—Probably The Charon name thing is starting to get to me. Every meeting, press brief, interview I hear the name of Pluto’s largest moon pronounced differently. I swear to Hades, sometimes I hear the same person pronounce it two ways.

Granted, I’m jet lagged, sleep deprived, and the coffee in the press room is lukewarm and from Dunkin’ Donuts (what gives, NASA?), but I’m starting to feel like someone is messing with me. So I started asking people—mostly people wearing black polos emblazoned with the nine-sided New Horizons logo: “How do you pronounce the name of Pluto’s largest moon?” I didn’t get far enough to get meaningful survey results, but I did find out why the results would always be mixed. That’s because I ran into Will Grundy, one of New Horizons’ co-investigators and an astronomer at Lowell Observatory. “Well, the original Greek way to pronounce it would be Gheghron,” he says, shoving the word out of the back of his throat like it’s a big, fat Klingon loogie. Gross, but makes sense. After all, Charon was the ferryman who brought damned souls across the river Styx into Pluto’s realm. But the astronomer who gave the moon its name didn’t even know about the Greek myth when he picked the name1.

Jim Christy, who discovered the moon in 1978, had promised his wife Charlene he would name the object after her. See, his wife’s name is Charlene, so he took her nickname—Char—and threw an -on in on the end to science things up. Some of his colleagues had been lobbying to name the moon Persephone (Pluto the god’s abducted queen), so he started doing some research. That’s when he stumbled across the Greek myth, and with that argument in hand the astronomical community informally adopted Charon later that year, and then formally in 1985. So what’s that got to do with the pronunciation? Most astronomers, says Grundy, pronounce it “Share-on, as a tip of the hat to Jim and his wife.” But then he shrugs and says everybody flops back and forth all the time. “We all say it both ways in a single sentence.” Really? Guys, that is a hell of a way to come up with nomenclature. Lunacy, even. 1 Update 14:26 ET July 20 2015.

This Sky & Telescope article from 2008 has the entire naming episode in full detail. NASA Releases Stunning Color Images of Pluto and Charon NASA/JHUAPL/SWRI Holy moly what a press conference we just had here at Pluto central. Alan Stern unleashed his science officers with new images and new science, and the first to drop were the highest resolution color pics of Pluto and Charon yet. Each shows some pretty cool stuff. For Pluto, the biggest revelation is that the big heart is actually two different colors. Those colors (exaggerated for contrast) indicate different geologic, tectonic, or morphologic origins. And the rest of the visible world is a mosaic of patina. “Some regions are relatively ancient, and other places are very young and currently undergoing geologic evolution,” said Jeff Moore, the New Horizons team scientist from NASA Ames who presented the images. But characteristic of the New Horizons team, Moore was guarded on the details. He said he’s waiting for stereographic data—which will show relief—before speculating any further on what might be happening on the dwarf planet’s surface.

For instance, the heart’s left lobe currently looks as smooth as a cherub’s cheek, but some cratering might show up at higher resolutions. The information from Charon is probably even more surprising. See that big blob of red? That stuff came from Pluto. “Charon does not have an atmosphere that is known so far,” says Will Grundy, a New Horizons team scientist and astronomer at Lowell Observatory. Charon may not have an atmosphere, but Pluto is leaking nitrogen like crazy . And as those nitrogen particles leave Pluto, Grundy says they could be getting dragged into Charon’s gravity. The distribution over the moon would be about even. But while nitrogen particles will burn away on the always-sunny equatorial and midlatitude regions, those that land on the polar night side are in the dark for decades. If this hypothesis is correct, the chemical processes in the nitrogen would stain the underlying rock red. Grundy says he is waiting to see the other side of Pluto to see if that side is also red.

“The prediction should say that the other pole looks really similar.” Pluto's Moons | Five Satellites of Pluto Pluto's Moons | Five Satellites of Pluto By Tim Sharp, Reference Editor | February 23, 2016 11:00am ET MORE These close views of Pluto's four smaller moons were captured by NASA's New Horizons probe during its historic July 2015 flyby. Data from New Horizons suggests that at least two (and maybe even all four) were born from mergers of even smaller moons. Credit: NASA/JHUAPL/SwRI Pluto, the dwarf planet that was once considered the ninth planet, has a growing entourage of satellites. The tiny world has five moons of varying size in orbit around it that tumble and dance in a strange and chaotic pattern. "The way I would describe this system is not just chaos, but pandemonium," Mark Showalter, a co-investigator on the New Horizons mission, said at a press conference last November. To the surprise of many, NASA's New Horizons mission did not turn up any additional moons during its historical flyby.

Charon, Pluto's largest companion Pluto has one very large moon that is almost half the planet’s size. Discovered in 1978, it was named Charon after the demon who ferried souls to the underworld in Greek mythology. (Pluto is named for the god of the underworld.) The huge size of Charon (750 miles or 1,200 kilometers in diameter) sometimes leads scientists to refer to Pluto and Charon as a double dwarf planet or binary system. Pluto's diameter is 1,473 miles (2,370 km). Pluto and Charon are just 12,200 miles (19,640 km) apart, less than the distance by flight between London and Sydney, Australia. Charon's orbit around Pluto takes 6.4 Earth days, and one Pluto rotation — a Pluto day — also takes 6.4 Earth days. This means Charon hovers over the same spot on Pluto's surface , and the same side of Charon always faces Pluto, a phenomenon known as tidal locking.

NASA's New Horizons spacecraft obtained this high-resolution enhanced color view of Pluto's moon Charon just before the closest approach on July 14, 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute While Charon is mostly gray, its northern pole has a reddish tint. Most of the moon is covered with water-ice, but the red region is likely made up of shredded pieces of Pluto's atmosphere. The moon has a surprisingly young surface, suggestive that it once housed an ocean in its interior, one that would have long ago frozen. Compared with most of solar system's planets and moons, the Pluto-Charon system is tipped on its side in relation to the sun. Also, Pluto's rotation is retrograde compared to the other worlds — it spins backwards, from east to west. Two smaller moons In 2005, as scientists photographed Pluto with NASA's Hubble Space Telescope in preparation for the New Horizons mission — the first spacecraft to visit Pluto and the Kuiper Belt — they discovered two other tiny moons of Pluto, now dubbed Nix and Hydra . These are two to three times farther away from Pluto than Charon.

While NASA's New Horizons mission was able to capture significant details about Charon during its 2015 flyby, it was only able to view the other four moons from a distance. Still, it provided the best look at the satellites to date. The spacecraft revealed details as small as 2 miles (3 km) on Nix and 0.7 miles (1.2 km) on Hydra. The mission also provided the best measurements for the tiny moons. Nix is estimated to be 26 miles (42 km) long and 22 miles (36 km) wide, while Hydra is 34 miles (55 km) in length. Hydra has a shape resembling a mitten or a rubber duck with at least two large craters. The moon resembles Comet 67P/Churyumov–Gerasimenko, which Europe's Rosetta mission has been orbiting since August 2014. Scientists think that Comet 67P may have formed when two separate bodies merged, and the same process may have played a role in the formation of Hydra. Hydra was the nine-headed mythological serpent that guarded Pluto's realm.

The irregularly shaped Nix looks much like a jellybean, with a surprisingly big impact crater. It is not as bright as Pluto, though brighter than Charon. In Greek mythology, Nyx was the goddess of the night and mother of Charon. The spelling was changed to Nix, the Egyptian goddess of night and darkness, to avoid confusion with two asteroids of the same name. "Nix isn't very large, and there is a very fine line between an impact that will make a crater that big and one that will break Nix apart," New Horizons team member Simon Porter, of the Southwest Research Institute in Boulder, Colorado, wrote in a blog post . "So, either Nix was very lucky in surviving that collision, or it's a fragment of an older moon that was somehow destroyed." All four of the small moons appear to be coated by relatively pure water-ice. Fourth and fifth moons Scientists using Hubble discovered a fourth moon, Kerberos, in 2011. New Horizons revealed that the moon has two lobes, one about 5 miles (8 km) wide and the other about 3 miles (5 km) in diameter. Like Hydra, it may have formed from the merger of two separate objects.

Kerberos orbits between Nix and Hydra. Despite its small size, Hubble observations revealed that it exerts a strong gravitational influence on the neighboring moons. Before New Horizons arrived, scientists thought the moon might be large but dark, keeping it obscured. Instead, the moon is small and bright. The moon was named for the three-headed dog in Greek mythology (Cerberus to the Romans). The fifth moon, spotted in 2012, is named Styx after the river separating the living from the dead. It is estimated to be irregular in shape and 4.5 miles (7 km) wide. It is in a 59,030-mile (95,000-km) diameter circular orbit around Pluto that is assumed to lie in the same plane as Pluto’s other known moons. Scientists anticipated the discovery of more moons when New Horizons arrived at Pluto, but none were spotted. Collision debris Pluto's entire moon system is thought to have formed by a collision between Pluto and a similar-size body early in the history of the solar system. The collision threw out material that coalesced into the family of satellites orbiting Pluto. New Horizons found that the four moons were surprisingly chaotic.

Hydra is the fastest-rotating, spinning once every 10 hours during its 38-day orbit of Pluto, or 89 times every orbit. "If Hydra were spinning much faster, material would fly off its surface due to the centrifugal force," Showalter said in a statement from NASA. The other three moons rotate between 6 to 10 times during their orbit, which is still surprisingly fast. In addition to that, Nix is tilted on its axis by 132 degrees and rotating backward. Such rapid rotations are surprising because the gravity of Pluto should slow down the spin of the smaller moons. "The question is, why [don't they] slow down? It's not so much why [are they] so fast. … There's clearly something fundamental about the dynamics of the system that we do not understand," Showalter said in the statement. Additional reporting by Nola Taylor Redd, Space.com Contributor. Follow Nola on Twitter @NolaTRedd or Google+ . Follow us at @Spacedotcom , Facebook or Google+ . Originally published on Space.com . NASA - What Is Pluto? What Is Pluto?

Words to know: astronomer: a scientist who studies the planets, stars and space Astronomical unit (AU): the average distance from the sun to Earth -- about 93 million miles (149 million kilometers). Earth is 1 AU from the sun. elliptical: shaped like an ellipse, which is a symmetrical oval where both ends are the same size, like a racetrack Pluto was discovered in 1930 by U.S. astronomer Clyde Tombaugh. For many years, Pluto was called a planet. It was the smallest planet in the solar system and the ninth planet from the sun. Today, Pluto is called a dwarf planet. A dwarf planet is round and orbits the sun just like the eight major planets. But unlike a planet, a dwarf planet does not have enough gravity to attract all of the space dust and tiny objects in its path. A dwarf planet also is much smaller than a planet, but it is not a moon. On average, Pluto is a distance of approximately 39.5 astronomical units, or AU, from the sun. That is almost 40 times farther from the sun than Earth is.

Because of its elliptical orbit, Pluto's closest point to the sun is 29.7 AU. This means that Pluto is sometimes closer to the sun than the planet Neptune. Pluto's farthest point away from the sun is 49.7 AU. Pluto is in a region called the Kuiper (KY-per) Belt. The Kuiper Belt is a large band of thousands of small, icy objects that orbit the sun beyond Neptune. Pluto is only 1,400 miles (2,300 kilometers) wide. That is about half the width of the United States and slightly smaller than Earth's moon. It takes Pluto 248 years to make one revolution around the sun. Pluto takes 6 1/2 days to rotate, so one day on Pluto is about 6 1/2 days on Earth. In 2005, this image from NASA's Hubble Space Telescope was used to identify two new moons orbiting Pluto. Pluto is in the center. The moon Charon is just below it. The newly discovered moons, Nix and Hydra, are to the right of Pluto and Charon. Image Credit: NASA, ESA, H.

Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team View Larger Image → In the same year that it was discovered, an 11-year-old girl from England suggested it be named "Pluto" after the Roman god of the dead. Pluto has three known moons. Its largest moon, named Charon (KER-ən), is about half the size of Pluto. Astronomers discovered Pluto's two other moons -- Nix and Hydra -- in 2005 using images from NASA's Hubble Space Telescope. Nix and Hydra are very small. Scientists believe the moons are less than 100 miles (160 kilometers) wide. Why Is Pluto No Longer Called a Planet? In 2003, U.S. astronomer Mike Brown discovered a new object beyond Pluto. Brown thought he had discovered a new planet because the object, which he named Eris (EER-is), is larger than Pluto. The discovery of Eris caused other astronomers to talk about what makes a planet a "planet." The International Astronomical Union is the group of astronomers responsible for naming objects in space.

The IAU decided that Pluto and objects like it were not really planets at all because of their size and location in the solar system. The IAU decided that Pluto and objects like it should now be called dwarf planets. Pluto also is called a plutoid. A plutoid is a dwarf planet that is farther out in space than the planet Neptune. The three known plutoids are Pluto, Eris and Makemake (MAH-kee-MAH-kee). A drawing of the solar system shows Pluto's tilted orbit. Pluto's orbital path angles 17 degrees above the line, or plane, where the eight planets orbit. Credit: NASA View Larger Image → Astronomers continue to study the solar system. They use high-power, ground-based telescopes to discover new objects in space. Ideas about the universe and Earth's place in it keep changing as scientists get new information. This can cause scientists to rethink what they know and how they classify objects. Scientists are still considering what makes an object a planet as they learn more about the most distant objects in the solar system. What Is Pluto Like? It is very, very cold on Pluto. Scientists believe the temperature on Pluto is 375 to 400 degrees below zero.

Pluto is so far away from Earth that scientists know very little about what the surface is like. Because of the cold temperatures, Pluto is probably covered with frost and ice. Pluto has about one-fifteenth the gravity of Earth. That means a person who weighs 100 pounds on Earth would weigh only 7 pounds on Pluto. Most of the other planets orbit the sun in a near-circle with the sun in the center. But Pluto's orbit is an ellipse, and the sun is not in the center. Pluto's orbit is also tilted compared to the orbits of the planets. The path on which Pluto orbits is angled 17 degrees above the line, or plane, where other planets orbit. An artist's drawing shows the New Horizons spacecraft as it nears Pluto. The moon Charon is in the distance. Image Credit:Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI) View Larger Image → How Is NASA Exploring Pluto Today? NASA has learned a lot about Pluto from studying images taken by the Hubble Space Telescope. Scientists used Hubble photos to discover the moons Nix and Hydra in 2005.

Hubble also has taken pictures of Pluto's surface showing dark and light areas. Even with the powerful Hubble telescope, the images are still fuzzy. In 2006, NASA launched New Horizons, which is the first mission to Pluto. New Horizons is a spacecraft about the size of a piano that is flying to the outer edge of the solar system. The spacecraft will take nine years to reach Pluto. In 2015, New Horizons will spend more than five months studying Pluto and its moons. New Horizons has cameras that will take pictures of Pluto. It also has scientific instruments that will gather information about Pluto. These pictures and data will help scientists know more about what Pluto is like. After it has finished studying Pluto and its moons, New Horizons will study objects deeper in the Kuiper Belt. Why Is NASA Exploring Pluto? Exploring planets is a historic endeavor and a major focus of NASA. Spacecraft have visited all eight planets in the solar system. Studying Kuiper Belt objects like Pluto may help scientists learn more about how planets form.

More About Pluto: Night Falls on Pluto's Largest Moon Charon - Seeker Feb 2, 2016 01:20 PM ET Night Falls on Pluto's Largest Moon Charon Pluto's largest moon, Charon, is cloaked in darkness, with just a tiny sliver lit up by the distant sun, in a newly released photo. Previous Next NASA/JHUAPL/SwRI NASA's New Horizons spacecraft captured this image of the night side of Pluto's largest moon, Charon, on July 17, 2015. Previous Next NASA/JHUAPL/SwRi Newly returned pictures taken by NASA’s New Horizons spacecraft are giving scientists -- and the rest of us -- the most detailed views of Pluto’s stunningly diverse landscape. “We continue to be amazed by what we see,” NASA chief scientist John Grunsfeld said in a statement. The latest images form a strip 50 miles wide and were taken when New Horizons was about 15 minutes away from its closest approach to Pluto on July 14.

Previous Next NASA/JHUAPL/SwRi As NASA’s New Horizons spacecraft raced toward a July 14 close encounter with Pluto, the probe’s telescopic long-range camera got to work on a sequence of pictures that revealed features smaller than half of a city block. Pluto’s surface turned out to be unexpectedly diverse, evidence of a complicated and rich geology. The mosaic pictured here starts about 500 miles northwest of Pluto's smooth Sputnik Planum region and covers the rugged al-Idrisi mountains, the shoreline of Sputnik Planum and its icy plains. This image has been scaled and rotated, for the full, high-resolution view, Previous Next NASA/JHUAPL/SwRi Scientists aren’t sure yet how some of Pluto’s craters came to contain layers, such as the one picture here in the upper right. “Layers in geology usually mean an important change in composition or event, but at the moment New Horizons team members don’t know if they are seeing local, regional or global layering,” NASA said.

New Horizons’ Long Range Reconnaissance Imager (LORRI) took a series of images about 15 minutes before the spacecraft’s July 14 close encounter with Pluto. The dark crater at the center of the image is apparently younger than the others because material thrown out by the impact is still visible. Most of the craters are within a 155-mile wide region known as Burney Basin, the outer rim of which appears as a line of hills at the bottom of this image. Previous Next NASA/JHUAPL/SwRi New Horizons gathered a 50-mile-wide view of Pluto’s rugged northern hemisphere, including a 1.2-mile high cliff, seen here from the left to the upper right, during a series of pictures taken by the spacecraft’s telescopic Long Range Reconnaissance Imager (LORRI) on July 14. The cliff is part of a canyon system that stretches for hundreds of miles across Pluto’s northern hemisphere. Scientists believe the mountains in the middle are comprised of water ice that has been changed by the motion of nitrogen or other exotic ice glaciers over the eons.

At the bottom of the image, which was taken when New Horizons was about 10,000 miles from Pluto, the badlands meet the giant icy plains of Sputnik Planum. Previous Next NASA/JHUAPL/SwRi Blocks of ice, upper left, appeared to be jammed together in an area the New Horizon scientists are calling the al-Idrisi mountains. Some of the mountains seem to be coated with a dark material, while others are bright. Scientists think material crushed between the mountains may be from the ice blocks jostling back and forth. The mountains end at the shoreline of a region named Sputnik Planum, which is marked by soft, nitrogen-rich ices that form a nearly flat surface. New Horizon’s Long Range Reconnaissance Imager (LORRI) took a series of images in the span of about one minute at 11:36 Universal Time on July 14, about 15 minutes before the spacecraft’s closest approach.

Pluto’s Large Moon Charon Is Stunning – Phenomena: No Place Like Home Pluto’s Large Moon Charon Is Stunning Posted Sun, 07/12/2015 Remember when we reported that Charon would probably turn out to be an astonishing world in its own right ? Well, the newest image released by the New Horizons team suggests Pluto’s largest moon is absolutely that. Charon is a world of chasms and craters, capped by a darkened pole. NASA/JHUAPL/SwRI In the photo, shot from less than 5 million kilometers away, the 1,200-kilometer-wide sphere appears riven with enormous canyons — at least one of which is deeper and longer than the Grand Canyon, said planetary geologist Bill McKinnon of the Washington University in St. Louis in a statement. In addition, Charon’s surface is mottled with impact craters. That alone is not surprising (in fact, craters were one of the team’s top predictions for surface features on Charon), but the size and color are intriguing.

One of the crater bottoms appears darker than the surrounding surface; whether this is because it’s made of different material or is simply less reflective isn’t clear yet. And then there’s that mysteriously dark region capping the moon’s pole. What is clear is that these images will only get better as New Horizons continues to speed toward its July 14 trip through the Pluto system . Soon, we may even be able to see the planet’s four small moons as well. ( Learn more about the historic mission to Pluto on the National Geographic Channel. ) Speaking of moons, one of the predictions the team made was that New Horizons would discover at least one more moon orbiting Pluto. So far, no additional moons have been spotted. Unfortunately, that could be due to the July 4 glitch that sent New Horizons into safe mode. “The one piece of significant science that we did lose due to the safing event was the deepest search for moons,” says team member Mark Showalter of the SETI Institute. Those data would have been taken seven days prior to closest approach. Now, the team will be searching through older data (from 13 days prior) for moons. Those images are taken from about twice as far away, though.

But all hope is not lost yet. New moons might still be discovered, Showalter says, either during the reprocessing of data taken in the last month, or if a new moon serendipitously pops up in another image. 11 thoughts on “Pluto’s Large Moon Charon Is Stunning” Jay L. Stern says: Size of Pluto’s Moon Charon Pinned Down Size of Pluto’s Moon Charon Pinned Down By Robert Roy Britt | January 4, 2006 01:00pm ET MORE Artist's impression of Pluto and Charon as seen from one of Pluto's other moons. Credit: David Aguilar/Center for Astrophysics A new study provides the best estimate to date of the diameter and heft of Pluto's moon Charon and suggests the satellite likely has no atmosphere. Charon is the largest known moon in relation to the size of its host planet. It is about half the size of Pluto and about eight times less massive. The new observations put Charon's diameter at between 750 and 753 miles (1,207 and 1,212 kilometers).

Charon's density is 1.71 times that of water, which suggests its icy contents are just more than 50 percent rock, and about 10 percent less rock by mass than Pluto. Ironically, Charon's density is now known more precisely than that of Pluto. To take Charon's measure, astronomers used three telescopes to monitor an occultation, in which Charon eclipsed the light of a background star for about a minute. Only one other such rare event involving Charon has been witnessed. Pluto is known to have a very thin atmosphere, based on other occultation observations. If Charon has one, the new observations indicate, its pressure would be less than one-sixth of a millionth of the air pressure at the surface of the Earth. That would be 100 times less than the air pressure at Pluto's surface. "Comparing Pluto and Charon, we seem to cross a borderline between bodies which may have bound atmospheres—like Pluto—and airless bodies like Charon," said Olivier Hainaut of the European Southern Observatory. The research is detailed in the Jan. 5 issue of the journal Nature.

The leading theory for the formation of Pluto and Charon, along with two other small moons recently discovered, is that one object collided into another and the system coalesced out of the remains. "Our observations show that there is no substantial atmosphere on Charon, which is consistent with an impact formation scenario," said MIT researcher Amanda Gulbis, lead author of one of two papers in the journal. Pluto Colder Than Expected Pluto has moons. One of the moons is very large. The large moon is named Charon . The other two moons are fairly small. They don't really have names yet. For now they are called S/2005 P1 and S/2005 P2. Charon is nearly as big as Pluto. Some astronomers call Pluto and Charon a double planet . James Christy discovered Charon in 1978. S/2005 P1 and S/2005 P2 were discovered in 2005. A team of astronomers led by Alan Stern and Harold Weaver found the moons. The team was looking for new moons of Pluto using the Hubble Space Telescope . They were getting ready for the New Horizons space mission to Pluto.

S/2005 P1 is about 150 km (93 miles) across. S/2005 P2 is even smaller, about 100 km (62 miles) across. S/2005 P1 takes 38 days to go around Pluto. S/2005 P2 orbits Pluto every 25 days. S/2005 P1 and S/2005 P2 will get "real" names after astronomers observe them a few more times. They want to make sure they are moons of Pluto before they give them permanent names. We don't know whether Pluto has rings or not. Nobody has seen any rings around Pluto so far. Last modified January 23, 2006 by Randy Russell . Shop Windows to the Universe Science Store! Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game ! Windows to the Universe Community News Pandemonium! Motion of Pluto's Moons Perplexes Scientists Pandemonium!

Motion of Pluto's Moons Perplexes Scientists Calla Cofield Share View photos The four smallest moons of Pluto are exhibiting very strange behavior, according to scientists with the New Horizons mission. More The orbits of Pluto's four smallest moons are even more chaotic than scientists had expected, according to new results from the New Horizons mission, which made a close flyby of Pluto in July. "The way I would describe this system is not just chaos, but pandemonium," Mark Showalter, a co-investigator on the New Horizons mission , said today (Nov. 9) during a news conference at the meeting of the Division for Planetary Sciences of the American Astronomical Society. "We honestly have not seen anything like this before, and we still don't know what to make of it." The new results show that as the four moons orbit Pluto and its largest moon, Charon, some of them are spinning incredibly fast, one is spinning backward against its orbit and some are tilted on their sides. This is in stark contrast to nearly every other moon in Earth's solar system, most of which are locked into a more rigid and unmoving orbit around their parent bodies, making Pluto's moons the wild children of the solar system.

[Watch: Pluto's Four Tiny Moons' Topsy-Turvy Tumbles ] Pluto has five moons. Its largest, Charon, has a diameter a little more than half that of its parent body. The two ice dwarfs experience what's known as tidal locking or synchronous rotation, meaning the same side of Charon forever faces the same side of Pluto, even as they orbit around a common point in space. This tight relationship earns them the title of "binary planet." This spinning duo is orbited by four smaller moons, which scientists only discovered recently, between 2005 and 2013. Using data from the Hubble Space Telescope , scientists showed earlier this year that the four moons are not tidally locked around Pluto and Charon, and that the system might be somewhat chaotic. But now that more data have come down from New Horizons, scientists say things in the system are beyond disorganized — and it's unexplainable. Showalter said during the news conference that scientists expected to see "little wobbles" in the orbits of the four moons, but instead, they're seeing extremely rapid rotation.

Hydra, the most distant of Pluto's moons, is spinning once every 10 hours during its 38-day cycle around Pluto, which means it spins 89 times every orbit. "If Hydra were spinning much faster, material would fly off its surface due to the centrifugal force," Showalter said in a statement from NASA. During the news conference, he said the other moons are rotating more slowly, but at a rate of six to 10 rotations per orbit around Pluto. "This is unprecedented," Showalter said at the news conference. "We simply have not seen a satellite system that does this." In addition to these rapid rotations, Pluto's second-closest moon, Nix, is tilted on its axis by 132 degrees and is rotating backward. Showalter clarified that it is not impossible to imagine that the moons would spin so rapidly following a collision with another object . What is so mysterious is that all four objects are spinning rapidly (it's difficult to imagine a collision that would affect all four of them), and that the gravitational pull of Pluto doesn't appear to have slowed them down, he said.

Typically, the gravity of a parent body would dissipate the planet's rotational motion, "and yet that's not what we're seeing, so that's really the puzzle," Showalter said at the news conference. "The question is, why [don't they] slow down? It's not so much why [are they] so fast." "There's clearly something fundamental about the dynamics of the system that we do not understand," Showalter said in the statement.

Question: What is the largest moon of Pluto?
Answer: Charon