Charon orbits Pluto in 6.3873 Earth days, following a circular path with a radius of 19,640 km (12,200 miles). The average distance between Charon and Pluto is 19,570 kilometres (12,160 mi).

Christy noticed that a slight elongation appeared periodically. Naval Observatory station in Flagstaff, Arizona. [17] It was discovered in 1978 at the United States Naval Observatory in Washington, D.C., using photographic plates taken at the United States Naval Observatory Flagstaff Station (NOFS). With four smaller satellites in orbit about the two larger worlds, the Pluto-Charon system has been considered in studies of the orbital stability of circumbinary planets. Before New Horizons' flyby, there were two conflicting theories about Charon's internal structure: some scientists thought Charon to be a differentiated body like Pluto, with a rocky core and an icy mantle, whereas others thought it would be uniform throughout. The color in the image has been enhanced to bring out differences in the features on the moon's surface.

The New Horizons spacecraft is the only probe that has visited the Pluto system. The Earth's diameter almost four times the diameter of the Moon. [34], Unlike Pluto's surface, which is composed of nitrogen and methane ices, Charon's surface appears to be dominated by the less volatile water ice. Charon synonyms, Charon pronunciation, Charon translation, English dictionary definition of Charon. Since the 1990s Pluto and Charon have come to be regarded as giant members of the Kuiper belt, a ring of icy, cometary objects that lies beyond Neptune’s orbit. Because neither object truly orbits the other, and Charon has 12.2% the mass of Pluto, it has been argued that Charon should be considered to be part of a binary system with Pluto. Today, however, ~TildeLink() is covered mainly by dark water ice, and Pluto mainly by bright methane ice. Astronomy The largest of Pluto's satellites. The International Astronomical Union (IAU) states that Charon is considered to be just a satellite of Pluto, but the idea that Charon might be classified a dwarf planet in its own right may be considered at a later date. This indicated a synchronous orbit, which strongly suggested that the bulge effect was real and not spurious. Professor of Astronomy, University of Hawaii at Manoa, Honolulu. The lack of such oblateness in Charon could mean that it is currently in hydrostatic equilibrium, or simply that its orbit approached its current one early in its history, when it was still warm. Any deviation from a perfect sphere is too small to have been detected by observations by the New Horizons mission. CallUrl('www>projectpluto>comhtm',1), period of the planet; a synchronous satellite with an orbital inclination of zero (same plane as the planet's equator) stays fixed in the sky from the perspective of an observer on the planet's surface (such orbits are commonly used for communications satellites; it is also seen in the cases of Pluto and ~TildeLink()).

Astronomer Mike Brown can be heard pronouncing it, United States Naval Observatory Flagstaff Station, Learn how and when to remove this template message, five-year period of mutual eclipses and transits, "NASA New Horizons: The PI's Perspective—Two for the Price of One", "New Horizons Team Names Science Ops Center After Charon's Discoverer", "Planetary Satellite Mean Orbital Parameters — Satellites of Pluto", "Measuring the Size of a Small, Frost World", http://www.johnstonsarchive.net/astro/tnos.html#LAR, "Why Pluto's Moon Charon Wears a Red Cap", "IAUC 3241: 1978 P 1; 1978 (532) 1; 1977n", "IAUC 4157: CH Cyg; R Aqr; Sats OF SATURN AND PLUTO", "Welcome to the solar system, Nix and Hydra! Charon is the largest moon of Pluto.

The brighter the object, the lower it is on the scale.

CallUrl('planetfacts>orgeverything2>compl?node=Astronomy',1), On August 30, 1992, David Hewitt, of MIT, and graduate student Jane Luu identified the first trans-Neptunian object found after Pluto and ~TildeLink(), (15760) 1992 QB1, which they discovered in the region that has since become known as the Kuiper Belt. CallUrl('www>skyandtelescope>comzoomschool>comshtml',0), This should reach Pluto and its moon ~TildeLink() between 2015 an 2017. CallUrl('stardate>orgcomorgphp?startrow=500',0), Pluto has its own relatively large and close moon, ~TildeLink(). Pluto and its largest moon, Charon (left), as seen by the New Horizons spacecraft. Pluto and Charon, to scale.

CallUrl('www>eso>orgcomastrodigital>orghtml',0), No other pair in the Solar System are so close in size (except for Pluto's main satellite, ~TildeLink(), but they are an unusual pair for a lot of other reasons that I will not discuss at this time). This means TESS will look at stars that are as bright or brighter than Pluto's moon ~TildeLink() appears to us. It was the best image of Charon to that date (4). This occurs when the Pluto–Charon orbital plane is edge-on as seen from Earth, which only happens at two intervals in Pluto's 248-year orbital period. Everything you always wanted to know. With half the diameter and one eighth the mass of Pluto, Charon is a very large moon in comparison to its parent body. Its diameter—1,208 km (751 miles)—is a little more than half that of Pluto, and its mass is more than one-tenth of Pluto’s mass. It was discovered telescopically on June 22, 1978, by James W. Christy and Robert S. Harrington at the U.S. *Sync. The hadrosaurid Charonosaurus is named in Charon's honor because it was found along the banks of the Amur River in the Far East. Charon also always shows the same hemisphere because it is in a state of synchronous rotation; that is, it spins on its axis in the same time it takes to orbit Pluto. Because of the high mass ratio, the barycenter is outside of the radius of Pluto, and the Pluto-Charon system has been referred to as a dwarf double planet. 2009; Rannou & Durry 2009; Olkin et al. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. This means that Charon's orbit has zero mean inclination with respect to Pluto's mean equator, which in turn means that Charon's mean right ascension of ascending node with respect to Pluto's mean equator is undefined. Charon is so large and massive with respect to Pluto that some scientists prefer to think of the two bodies as a double system. [25], There is minor debate over the preferred pronunciation of the name. It was fortuitous that one of these intervals happened to occur soon after Charon's discovery. [26][27] These indicate only the "k" pronunciation of "Charon" when referring specifically to Pluto's moon. 1989), later repeatedly observed via stellar occultations (e.g., Elliot et al. Later, when the area is again heated by the Sun as Charon's seasons change, the temperature at the pole rises to −213 °C, resulting in the volatiles sublimating and escaping Charon, leaving only the tholins behind. [48], The other moons of Pluto–Nix, Hydra, Kerberos and Styx–orbit the same barycenter but they are not large enough to be spherical and they are simply considered to be satellites of Pluto (or of Pluto–Charon).

This resulted in reassessments of Pluto's size, mass, and other physical characteristics because the calculated mass and albedo of the Pluto–Charon system had previously been attributed to Pluto alone. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.

CallUrl('www>enchantedlearning>comshtml',0), ~TildeLink()'s discovery also resulted in the calculation of Pluto's albedo being revised upward; since the planet was now seen as being far smaller than originally estimated, by necessity its capacity to reflect light must be greater than what had been formerly believed. [28], However, Christy himself pronounced the initial ch as a "sh" sound (IPA /ʃ/), after his wife Charlene. CallUrl('deepastronomy>space

Charon's discoverer James Christy and the children of Clyde Tombaugh were guests at the Johns Hopkins Applied Physics Laboratory during the New Horizons closest approach. ~TildeLink() was named after the mythological demon who ferried people across the mythological river Styx into Hades. Charon was discovered by United States Naval Observatory astronomer James Christy, using the 1.55-meter (61 in) telescope at United States Naval Observatory Flagstaff Station (NOFS). [39] In addition to Mordor, New Horizons found evidence of extensive past geology that suggests that Charon is probably differentiated;[37] in particular, the southern hemisphere has fewer craters than the northern and is considerably less rugged, suggesting that a massive resurfacing event—perhaps prompted by the partial or complete freezing of an internal ocean—occurred at some point in the past and removed many of the earlier craters. noun Astronomy The largest of Pluto's three satellites. Charon is just over half Pluto's size and orbits it so closely that it was not discovered as a distinct body until 1978. [36][37][38] The favored explanation for this phenomenon is that they are formed by condensation of gases that escaped from Pluto's atmosphere. Pluto and its moon ~TildeLink() are both TNOs, as are all the objects in the Kuiper Belt and the Oort cloud. The north polar region is dominated by a very large dark area informally dubbed "Mordor" by the New Horizons team. Pluto and three of its moons—Charon, Nix, and Hydra—as observed by the Hubble Space Telescope. The image reveals a mountain rising out of a depression. Charon. In 1994, the clearest picture of the Pluto-Charon system showed two distinct and well defined circles (3). CallUrl('astronomy>swin>edu>au