Charon: Moon or Dwarf Planet? - Farmers' Almanac Email Address: Verify Email: Thank you! You're all set to receive updates from the us! To make sure you receive our emails properly, you may want to add newsletter@farmersalmanac.com to your email address book. You are here: Home » Astronomy » Charon: Moon or Dwarf Planet? Charon: Moon or Dwarf Planet? by Jaime McLeod | Monday, August 22nd, 2011 | From: Astronomy The Debate Over Pluto: Is It A Planet Or Not? When Pluto was downgraded to a dwarf planet in 2006, astronomers began thinking in a new way about its largest moon, Charon. Charon was the first of Pluto’s four moons to be discovered, and its largest. Charon is believed to be more than half the diameter of Pluto. Because Charon is so large in comparison to Pluto, the two bodies actually revolve around one another, instead of Charon revolving around Pluto, as once believed. For this reason, some astronomers have proposed upgrading Charon to the status of dwarf planet.

Here are some more interesting facts about Charon: – Charon was first discovered on June 22, 1978, by astronomer James Christy at the United States Naval Observatory Flagstaff Station. The moon (or dwarf planet, as the case may be) was first seen as a bulge appearing on some photos of Pluto. The bulge wasn’t confirmed to be a moon until nearly a decade later, when the two bodies entered a period of eclipsing one another. – The surface of Charon probably a rocky core surrounded by an icy outer layer, similar to Pluto. The moon is believed to feature numerous active volcanoes that spew ammonia-rich water. – Astronomers do not know the composition of Charon’s atmosphere, or if it even has one. Many unknown details will become clearer in 2015, when New Horizons, the first spacecraft sent to explore Pluto and its moons, arrives at its destination. – Charon is about 750 miles in diameter, just over half the size of Pluto. – It takes Pluto and Charon about 248 Earth years to complete one orbit around the Sun, and about 6.5 Earth days to revolve around one another.

– The average distance between Charon and Pluto 12,160 miles. – Charon takes its name from the mythological ferryman who carried the dead across the River Styx to the realm of Hades (Pluto to the Romans), god of the underworld. Christy chose it because of its similarity to a nickname he had for his wife, Charlene. – The average surface temperature on Charon is around -390° F, a little colder than Pluto’s. – In addition to Charon, Pluto has three other moons, Nix, Hydra, and the as-yet-unnamed P4 (S/2011 P 1). Because Pluto and Charon revolve around one another, these other three moons orbit both bodies. – Charon cannot be seen with the naked eye, or with most consumer grade telescopes. It can really only be observed with some of the most powerful telescopes in the world. The first clear images of it were taken from space by the Hubble Space telescope. Whether Charon remains a moon or is eventually upgraded to a dwarf planet, it remains one of the most interesting objects in our solar system.

Jaime McLeod is a longtime journalist who has written for a wide variety of newspapers, magazines, and websites, including MTV.com. She enjoys the outdoors, growing and eating organic food, and is interested in all aspects of natural wellness. Articles you might also like... 1 comment 1 Clicking Here { 04.20.16 at 7:55 am } This interface generates visual and auditory feedback on an electronic device, wherein the human player reacts upon the images on the screen in order to achieve a certain on-screen goal or objective. The best part of Star Wars games is that they can easily be molded into different genres. 3) Desert to Sea Bundle (Bioshock, Bioshock 2, Spec – Ops The Line). 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 . Pluto has a moon, named Charon, that was discovered in - PHYSICS - 1305 View Full Document This is the end of the preview. Sign up to access the rest of the document. Unformatted text preview: Pluto has a moon, named Charon, that was discovered in 1978, due to periodic eclipses of the planet by the moon, and vice-versa.

Charon has a 82 c V Andersen, 2005 83 mass approximately 1/6 that of Pluto, which is a large mass for a satellite relative to the body it is orbiting. Kuiper Belt Objects Starting in 1992, significant numbers of Kuiper belt objects in orbits larger than that of Neptune have been discovered, thanks to very sensitive surveys that became possible due to the advances in electronic detectors at telescopes. There seem to be at least three distinct classes of such objects: 1. Classical Kuiper Belt Objects are in orbits that stay sufficiently far from Neptune that the planet is unable to make significant changes in their orbits. Curiously, there are very few of these objects in orbits with semi-major axis larger than 50 AU or so. 2. Scattered Kuiper Belt Objects are on fairly eccentric and inclined orbits, probably due to weak gravitational interactions with Neptune over times of billions of years. 3. Plutinos are in orbits that put them in the same 3 to 2 resonance with Neptune that Pluto is in.

(This means that it is probably reasonable to think of Pluto as simply the largest of this class of objects.) A few larger objects in the outer solar system are worth mentioning: Quaoar (pronounced Kwah-o-wahr) is a classical Kuiper Belt Object discovered in 2002, that has a diameter approximately half that of Pluto. Sedna was discovered in 2003 and probably has a diameter of between 1/3 and 1/2 that of Pluto. Sedna is in a very eccentric orbit with a semi-major axis of about 500 AU, and a closest approach to the sun of 76 AU. It appears that Sedna might be neither a Kuiper Belt or an Oort Cloud object, but instead lies on an orbit between the two. Orcus is a plutino discovered in 2004, which may have a diameter larger than either Quaoar or Sedna. 2003 UB 313 A scattered Kuiper belt object discovered in 2003, it is essentially the same radius as Pluto. It has a satellite, so eventually, a c V Andersen, 2005 84 mass will be measured for it.

The discovery of this object has added new fuel to the is Pluto a planet or not? controversy. Chapter 11 The Sun and Its Influence in the Solar System In this course, we are primarily interested in the properties of the Sun that can have significant effects on things elsewhere in the solar system. That is, we are largely interested in the external properties of the sun. In ph1306, we instead look more closely at the Sun as a star, and thus its internal properties. The Sun is the dominant object in the solar system in at least: It contains over 99% the solar systems mass, making it the dominant gravitational feature in the solar system.... Physics 1305 (Solar System Astronomy) Exam 3, Sample Questions Dr. Andersen There may exam3_sample Pluto/Charon The Kuiper Belt Pluto the Misfit Planet As we shall see, Pluto and its large moon Charon (pronounced shehr-on) do not fit into our simple picture of 2 types of planets: terrestrial and giant. But problems with our simple planet classification is less important than what Pluto and Charon have to tell us about the outer solar system.

Discoveries of Pluto and Charon Both Pluto and its moon Charon were discovered by US astronomers - Pluto was discovered by Clyde Tombaugh at Lowell Observatory in Flagstaff, Arizona, in 1930, as shown below, by comparing the motion of a faint object relative to the stars (just as, more recently, the Kuiper Belt objects). After Clyde Tombaugh died in 1997, a website was created in his memory. Charon was discovered by James Christy of the US Naval Observatory in 1978, in the photograph shown in Figure 12.15a Even with a good telescope and clear skies Pluto and its moon Charon are fuzzy objects. Figure 12.15b is a Hubble Space Telescope picture of Pluto and Charon taken in 1994 (go here for more information about this image). (1) What prompted the searches for a planet beyond Neptune? Why did astronomers think there might be additional planets? Were their suspicions justified in the end? Characteristics of Pluto and Charon There is no doubt that Pluto is small compared with the other planets. At the same time, compared with its parent planet, Charon is the largest moon in the solar system.

Here is a comparison of the sizes of Pluto and Charon with the United States (click on the picture to get a larger version): With such fuzzy images, even with the best telescopes, how we able to measure the sizes of Pluto and Charon? The opportunity was provided by a fortunate quirk of Pluto and Charon's orbits. The rotation axis of Pluto as well as Charon's orbit around Pluto are, like Uranus, aligned almost with the plane of its orbit: During the period from 1985 through 1990, Pluto and Charon would eclipse each other on a daily basis - a Pluto day, that is. These eclipses turned out to be very important, since observations of the eclipses (called "mutual events") led to the first accurate determination of Pluto' and Charon's sizes, and subsequently to surprising albedo maps of the surface. Here are albedo maps of Pluto based on these mutual eclipses of Pluto and Charon. Below are maps based on Hubble Space Telescope data. This synthetic image of Pluto is created by processing many Hubble Space Telescope observations of the planet (typical images are shown in the small insets on the upper left).

The dark and light regions could be due to different types of ices on the surface, or could be topological features. This surface map of Pluto's albedo is reconstructed by imaging the planet at different times during its day. (2) Compare the albedo maps derived from the mutual eclipses with the maps derived from Hubble data. Did the mutual eclipse researchers get roughly the same features as shown by Hubble? (e.g., compare where the light and dark regions are on Pluto in each case). The mutual eclipses of Pluto and Charon provide their sizes. Measurements of Charon's orbit gives us Pluto's mass. With these pieces of information models have been constructed of Pluto's interior (the interior of Charon is really little more than guesswork). (3) (a) HOW does Charon's orbit allow us to determine Pluto's density? (b) What are the densities of rock and of pure ice? (c) The density of Pluto is about 2 g/cm3--corresponding to about 70% rock and only 30% ice.

By comparing the density of Pluto with the densities of Charon and of the moons of Uranus and Neptune, would you judge Pluto to have more or less ice that is typical for small bodies in the outer solar system? (d) Compare the density of Pluto with that of Triton. (4) Compare the properties of Pluto and Charon listed above with the table of properties of terrestrial and giant planets, Table 8.2 of the textbook. Why Pluto is a "misfit" planet? Consider Pluto's size, orbit, moon, density, etc; Impact Origin Pluto and Charon are thought to have come together and collided--in a similar way that we believe the earth's Moon collided with the Earth and re-formed to form the Moon. This impact theory for the origin of Charon explains various 'strange' things about Pluto and Charon. One clue is the density of Pluto and Charon. (5) (a) Say Pluto had a lot more ice before it suffered a big impact, what would have happened to the ice during the impact? Would the density of Pluto increase or decrease due to the impact?

(b) What is believed to have happened to Triton that might similarly have led to Triton loosing ice and having a similar, more rocky composition as Pluto? Is Pluto a Planet? This topic has led to a major public debate. You have just listed why Pluto is a misfit - but some want to re-classify Pluto as an asteroid or "minor planet" instead of a planet. Is Pluto a Planet? (6) (a) What are some of the criteria that people use for deciding whether to call Pluto a planet or not? (b) Is this a scientific issue? (c) So, what do YOU think? Should Pluto be called a planet? The Kuiper Belt Pluto & Charon are not alone. Over the past 5 years over a hundred new objects have been discovered beyond the orbit of Pluto. These objects are listed and plotted as they are discovered. Lots of information can be found on the Kuiper Belt page of Dave Jewitt, the co-discoverer of the first Kuiper Belt object, including a movie sequence of its detection. The issue of why the outer solar system dramatically changes at 30 A.U. from 4 large giant planets to lots of small icy objects is hotly debated.

At stake is the understanding of how our solar system formed and evolved to be the way it is now--and whether we should expect other solar systems to be the same. (7) (a) Look at the plot above. The masses of outer solar system objects are plotted vs. distance from the Sun. The graph has scales that increase in powers of ten--with MASS (relative to earth) on the Y-axis vs. Distance from the Sun (in A.U.) on the X-axis. How many powers of 10 are there on each axis? (b) Note that the giant planets form a group that are 10-300 times the mass of the earth. Pluto, Charon and Triton form a group that is 0.001-0.01 times the mass of the earth--that is 0.1 to 1% of the earth's mass. The new "QB1" objects are about 10 to 100 times smaller than Pluto/Charon/Triton.

The smallest objects, comets, are found outside Pluto's orbit, greater than 50 A.U.--how many Kuiper Belt objects (such as QB1) does it take to add up to the mass of the Earth? (c) How many comets does it take to add up to the mass of the Earth? It is now thought that there are probably 1000s of small objects--with masses between the those of Pluto and comets--that orbit the Sun at distances between 50 and 100 A.U., forming a "fuzzy" disk in the ecliptic plane. This disk is named after the Dutch astronomer, Gerald Kuiper who proposed such a disk existed in the 1950s. These Kuiper objects are just now being discovered. The following SKETCH shows the outer planets and the location of the objects that we believe make up the Kuiper Belt. Pluto's orbit is shown in red. The four outer giant planets (Jupiter, Saturn, Uranus, and Neptune) have their orbits outlined in blue. (8) Using this picture and what you know about the sizes of the orbits of the outer planets (e.g.

Neptune's orbit is 30 AU from the Sun) how far away from the Sun are the objects at the inner edge of the Kuiper Belt? What about objects at the outer edge? Here is a MAP showing the actual location of the Kuiper Belt Objects discovered to date. The map is from the Minor Planets Center at the Harvard/Smithsonian Center for Astrophysics and is updated as new objects are found. Pluto Links - ( Here is a Pluto scientist's ranking of Pluto sites): 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 Two of Pluto’s Moons Get Names From Greek Mythology’s Underworld - The New York Times The New York Times Space & Cosmos |Two of Pluto’s Moons Get Names From Greek Mythology’s Underworld Search Continue reading the main story Photo An image, taken in 2012, by the Hubble Space Telescope of Pluto and its moons. The two small moons labeled P4 and P5 have been renamed as Kerberos and Styx. Credit Mark Showalter/SETI Institute; NASA; ESA, via Agence France-Presse — Getty Images For an astronomical body that circles the Sun but is not officially a planet, Pluto has a lot going on, out there four billion miles from the Sun where comets and other icy bodies roam. Among other things, Pluto has a retinue of at least five — count ’em, five — moons circling it. On Tuesday the International Astronomical Union announced names for two of these moons, the fourth and fifth to be discovered. Moon No. 4 is now Kerberos, after the many-headed dog that guarded the entrance to the underworld in Greek mythology.

Moon No. 5 is Styx, named for the river that souls had to cross over to get to Hades, or the underworld, and the goddess who ruled over it. Those names, of course, are familiar ones in the Plutonian family. In Greek mythology, Pluto, also known as Hades, was the lord of the underworld, a place that was also sometimes called Hades. Pluto’s other moons are Charon, named for the ferryman who carried dead souls across the river Styx; Hydra, a multiheaded monster that helped guard the entrance to the underworld; and Nix, the mother of Charon. In 2011 and 2012, Kerberos and Styx were discovered by a team led by Mark Showalter of the SETI Institute , which searches for extraterrestrial life, using the Hubble Space Telescope . Each is estimated to be 20 or so miles in diameter, making them the smallest of Pluto’s moons so far.

By astronomical tradition, the discoverer of a new planet or moon is entitled to suggest names for it to the International Astronomical Union, which has about 11,000 members in 93 countries and was founded in 1919 to promote international scientific cooperation. Advertisement Continue reading the main story Dr. Showalter, however, said he thought it would be more fun to throw it open to the public, and held an Internet contest in which people could vote for names for the moons. He was impressed, he said in an e-mail, by the amount of thinking and creativity that went into the suggestions. “There were a lot of weird names,” he wrote. “A few suggested ‘Potato and Potahto,’ which I thought was pretty funny. Lots of children wrote in to suggest their siblings as ‘minions of Hades.’ ” Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up Privacy Policy The favorite name turned out to be Vulcan, which is both the Greek god of fire and, perhaps more significantly, the home planet of Mr. Spock, the “Star Trek” character played by Leonard Nimoy. Dr.

Showalter submitted the names Vulcan and Cerberus — which was later changed to the Greek spelling Kerberos to avoid confusion with an asteroid — to the Working Group for Planetary Nomenclature and the Committee on Small Body Nomenclature of International Astronomical Union. The astronomical union rejected Vulcan because it had already been used as the name for a hypothetical planet between Mercury and the Sun, and it had no connection to the mythological underworld. Instead the moon-namers chose Kerberos and the next runner-up, Styx. It was not the first time that citizens with stars in their eyes had been disappointed by the astronomical union, which has a tangled history with Pluto. It was the union that, back in 2006, tossed Pluto out of the club of planets , after years of debate that reached into classrooms and planetariums. In an election at the union’s triennial meeting, in Prague, the group voted to define a planet as an object that was round, orbited the Sun, and had cleared everything else out of its orbital path. Pluto is round and circles the Sun but its region of the solar system is cluttered with thousands of small icy objects.

And so Pluto was demoted to being a “dwarf planet.” Tell it to Kerberos, Styx, Charon, Nix and Hydra. Correction: July 5, 2013 An article on Wednesday about the naming of two of Pluto’s moons misidentified the year in which Pluto was demoted from planet status. That decision, by the International Astronomical Union, took place in 2006, not in 2003. A version of this article appears in print on July 3, 2013, on Page A14 of the New York edition with the headline: Two of Pluto’s Moons Get Names From Greek Mythology’s Underworld. Order Reprints | Today's Paper | Subscribe Images of Pluto's moon Charon show huge fractures and hints of icy 'lava flows' Images of Pluto's moon Charon show huge fractures and hints of icy 'lava flows' October 6, 2015 by David Rothery, The Conversation Charon has a huge fracture system, unlike anything seen on Pluto.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Since the New Horizons probe flew through the Pluto system on July 14, most of the attention has been on Pluto itself. But it also has a comparatively large and – as we now know – fascinating moon called Charon. The vast haul of data from New Horizons is now being transmitted to Earth at a slow rate because the signal is so weak. Yet some amazingly detailed images have been released, helping researchers trace the moon's violent history through its ridges and craters. Charon is usually pronounced "Shairon" or even "Sharon", though "Kairon" would be a more faithful rendering of the name of the ferryman of the classical underworld after whom it is named. Charon and Pluto are locked in a tidal embrace that matches their rotation rates to their orbital period about each other, so that the same side of Charon always faces Pluto, and vice versa. Our prior understanding is that Charon's surface is mostly water-ice, tainted by ammonia and lacking the more exotic methane, carbon monoxide and nitrogen ices that so spectacularly coat parts of Pluto.

Charon is a darker, drabber world than Pluto when you see an identically processed image of each (below). Surface secrets But there is still plenty of variety across the face of Charon if you look for it. The image below is an enhanced colour view of Charon's Pluto-facing hemisphere, brightened up relative to the previous dark view, showing details as small as 2.9 km. The brown smudge over its north pole might be discoloured by tiny particles of tar that have somehow drifted across from the top of Pluto's atmosphere, though if so we can't yet explain their concentration around Charon's pole. Pluto (lower right) and Charon (upper left) identically processed. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute As a geologist, what interests me most is Charon's surface history. The north is more heavily cratered than the south, which tells us that the terrain in the north is older, whereas the south has been subjected to some kind of resurfacing process that has either erased or buried the older craters. While we can tell that Charon has been resurfaced more recently than parts of Pluto, we don't know the exact mechanism for this.

It could have to do with the tidal-heating interaction between Pluto and Charon, but few people expected such apparently recent tidal heating. If this were our own moon, we could use density of craters to work out a surface age in billions of years, because we know the rate at which impacts have occurred to form those craters. But because we don't know the rate of crater formation on Pluto, all we can say is that Charon's more densely cratered surfaces are older than the less densely cratered areas. Perhaps the most impressive aspect of Charon is the system of fractures that stretch right across the globe. The broad fracture in the right-centre of the globe in the previous view has been provisionally named Serenity Chasma, and is seen in more detail in the view below, which includes a mosaic of high-resolution images showing features as small as 0.8 km. There's a clue here as to what might have gone on. The ground surface on the south of Serenity Chasma has been heaved up and tilted away from the rift, and the old tilted surface disappears below a smooth younger surface with fewer craters than the northern terrain.

So, maybe, the original surface was arched up over the rift and became split as the rift opened, and something smooth came flooding out. That could easily be "lava flows" made of an ammonia-water mixture erupted from Charon's interior, in a process called " cryovolcanism " to distinguish it from the much hotter volcanism on Earth. Some much narrower cracks crossing those plains also demonstrate a later phase of fracturing. Charon - the movie Part of Charon in the highest resolution yet available. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute The New Horizons team has used images obtained from different viewpoints to make a stereoscopic model of parts of Charon's surface, from which they constructed the artificial fly-over video below. It starts high above the north pole , swoops down to fly along the length of Serenity Chasma, and ends with a view across the cryovolcanic plains towards a moated mountain in the distance. Cousin moons Are there other worlds out there like Charon? Well, maybe some of the moons of Uranus , which have ammonia mixed with their water-ice too.

At 1207km in diameter, Charon is a little larger than Ariel but considerably smaller than Titania . All three have about 1.6 to 1.7 times the density of water, so they must contain about the same proportion of rock in their interiors. The video will load shortly During the only fly-by of Uranus (by Voyager 2 in 1986) we found that the globes of both Ariel and Titania are crossed by giant fracture systems and there are signs of cryovolcanic resurfacing on Ariel. The trouble is that we saw Uranus's moons much less well than we have now seen Charon, and the Voyager images, which seemed staggeringly detailed 30 years ago, are now frustratingly limited. But Charon shows us that Ariel and Titania are likely to be more complicated than they seem. Maybe it's time for another probe to explore the wonders around Uranus. Voyager 2 views of two icy fractured moons of Uranus that are most similar to Charon. Left: Ariel, 1155 km diameter. Right: Titania, 1576 km diameter. Credit: NASA/JPL What Are Pluto's Moons Named?

| Video What Are Pluto's Moons Named? | Video By Steve Spaleta | July 2, 2013 05:56pm ET Charon, Nix and Hydra have been joined by the recently named Kerberos and Styx, forming a pantheon of underworld figures from Greek mythology. Pluto's family turns out to be a fascinating bunch of objects. credit : SPACE.com NASA gives Pluto's 'heart' a name, reveals second riveting shot of dwarf planet - CNET CNET NASA gives Pluto's 'heart' a name, reveals second riveting shot of dwarf planet NASA gives Pluto's 'heart' a name, reveals second riveting shot of dwarf planet In a just-held briefing, NASA says that Pluto's "heart" will be named for the dwarf planet's original discoverer, a dark spot on moon Charon is called "Mordor," and Pluto is a relative newborn. Up Next The robots are coming to CES, and we can't wait to meet them This shot shows just one tiny sector of Pluto's surface in amazing detail.

And there's much more to come.Photo by NASA-JHUAPL-SwRI Tuesday, the New Horizons spacecraft thrilled us with the first high-quality shot the world had ever seen of Pluto. We were promised that there would soon be another image of even greater quality, and that's what NASA just delivered at a press conference at the Johns Hopkins Applied Physics Lab. Related stories Surprise! Pluto is bigger than scientists thought The image above shows an incredibly zoomed-in shot of the bottom portion of Pluto. According to NASA's science mission chief, John Grunsfeld , at this resolution it would be possible to see the JHAPL were it on the planet's surface. While there are no buildings on Pluto, thanks to the new image, the researchers were able to see that the planet does have icy mountains stretching as high as 11,000 feet. Perhaps even more significantly, because of the lack of impact craters in this area of the planet, the team is surmising that Pluto is relatively young -- probably less than 100 million years old. In addition to the new shot of Pluto, NASA also released this image of its moon Charon.

The dark spot at the top of Pluto's moon Charon is being called "Mordor."Photo by NASA-JHUAPL-SwRI Mission Operations Manager Alice Bowman said that the shot "blew our socks off." She then went on to explain some of the features in the image. She said the dark spot at the top of the moon -- which the team is informally calling "Mordor," after the black volcanic plane in the "Lord of the Rings" tales -- is likely a thin veneer. In the southwest area, Bowman said, a series of troughs and cliffs are visible that extend for 600 miles across the moon, and at approximately the two o'clock spot on Charon's edge, a canyon plunging four to six miles deep is also visible. "There is so much science in this image alone," Bowman said, promising that an image that will have five times the resolution is coming soon. A slightly smaller bit of news is that the following image was also released, of Pluto's moon Hydra.

It might not look like much to you or me, but it's pretty good considering New Horizons was 400,000 miles away when it was taken.Photo by NASA-JHUAPL-SwRI Though it's not as captivating as the other shots being returned by New Horizons, it was enough for NASA researchers to pinpoint the moon's size, which they'd thought could have been anywhere between 20 to 100 miles across. Turns out that it's 28 x 19 miles, so "Hydra is not a planet," as Hal Weaver , New Horizons project scientist, joked. 11 New Horizons' journey to Pluto (pictures) The other big news of the day is that NASA announced that the big heart-shaped patch of frost on Pluto, which so many of us are now familiar with, will be called Tombaugh Regio, after Clyde Tombaugh , the American astronomer who discovered Pluto in 1930. The announcement drew the biggest cheers. More data will continue streaming in from New Horizons over the next 16 months, so the discoveries are really just beginning.

Question: What has a moon named Charon?
Answer: Pluto