The planet Pluto has three known moons. The largest, Charon is larger than any other satellite compared to its planet. The other two moons, as yet unnamed, are much smaller. Their discovery was announced on 2005 October 31. Jump to: navigation, search Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... Jump to: navigation, search A planet in common parlance is a large object in orbit around a star that is not a star itself. ... Jump to: navigation, search 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... Jump to: navigation, search October 31 is the 304th day of the year (305th in leap years) in the Gregorian Calendar, with 61 days remaining, as the final day of October. ...

Pluto's satellite system

The orbits of the Plutonian system as seen from Earth, estimated from the discovery images of the outer moons.

The innermost moon, Charon, was discovered by James Christy on 1978 June 22, nearly half a century after Pluto. Two outer moons were imaged by the Hubble Space Telescope Pluto Companion Search Team on 2005 May 15, and precovered from Hubble images taken in June 2002. The team has scheduled further Hubble observations for February 2006. Once the orbits are confirmed, the International Astronomical Union can consider names for the outer moons. Given the sensitivity of the Hubble images, and the fact that the entire region of space dominated by Pluto's gravitational field was imaged, Pluto is not expected to have any other moons larger than approximately 20 km in diameter. Jump to: navigation, search Image File history File links Pluto_system. ... Jump to: navigation, search Image File history File links Pluto_system. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... James Walter Christy (born 1938) is an American astronomer. ... Jump to: navigation, search 1978 (MCMLXXVIII) was a common year starting on Sunday (the link is to a full 1978 calendar). ... Jump to: navigation, search June 22 is the 173rd day of the year (174th in leap years) in the Gregorian Calendar, with 192 days remaining. ... Jump to: navigation, search The Hubble Space Telescope is a telescope in orbit around the Earth. ... Jump to: navigation, search 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... Jump to: navigation, search May 15 is the 135th day of the year in the Gregorian Calendar (136th in leap years). ... Precovery is a term used in astronomy that describes the process of finding the image of an object (usually a minor planet) in old archived images or photographic plates, for the purpose of calculating a more accurate orbit. ... Jump to: navigation, search 2002(MMII) is a common year starting on Tuesday of the Gregorian calendar. ... Jump to: navigation, search 2006 is a common year starting on Sunday of the Gregorian calendar. ... Jump to: navigation, search Logo of the IAU The International Astronomical Union (IAU) unites national astronomical societies from around the world. ...

Pluto and Charon have been called a double planet because Charon is massive enough in comparison to Pluto that Pluto orbits the system's barycenter at a point outside its surface (see animation and barycenter for more animations). Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The term double planet has several accepted usages. ... The barycenter (from the Greek βαρύκεντρον) is the center of mass of two or more bodies which are orbiting each other, and is the point around which both of them orbit. ... The barycenter (from the Greek βαρύκεντρον) is the center of mass of two or more bodies which are orbiting each other, and is the point around which both of them orbit. ... Jump to: navigation, search Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ...

The Plutonian system has not been visited by spacecraft, but a flyby by the New Horizons mission is planned for 2015. New Horizons New Horizons is a NASA unmanned spacecraft designed to fly by Pluto and its moon Charon and transmit images and data back to Earth. ... Jump to: navigation, search 2015 is a common year starting on Thursday of the Gregorian calendar. ...

Table of known moons

The Plutonian moons are listed here by orbital period, from shortest to longest. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted. Pluto has been added for comparison, for it orbits a point outside itself. Gravitational collapse in astronomy is the sudden inward fall of a massive body under the influence of the force of gravity. ... Jump to: navigation, search A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ...

The diameters of objects can be estimated from their assumed surface reflectivity (albedo). The low estimates correspond to a 35% albedo like Charon, while the larger ones correspond to the 4% albedo of the darkest KBOs. Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... Jump to: navigation, search Discovery images of S/2005 P 2. ... Jump to: navigation, search Discovery images of S/2005 P 1. ... The albedo is a measure of reflectivity of a surface or body. ... The Kuiper belt (KYE per) is an area of the solar system extending from within the orbit of Neptune (at 30 AU) to 50 AU from the sun, at inclinations consistent with the ecliptic. ...

Further observations will determine if S/2005 P 2 and S/2005 P 1 are in orbital resonance with Charon and Pluto. Their currently estimated periods are four and six times that of the Charon-Pluto orbital period. In celestial mechanics, orbital resonance occurs when two orbiting bodies have periods of revolution that are in a simple integer ratio so that they exert a regular gravitational influence on each other. ...

See also

• Jupiter's natural satellites
• Saturn's natural satellites
• Uranus' natural satellites
• Neptune's natural satellites

• Solar System

• Timeline of natural satellites
• Naming of natural satellites

Jump to: navigation, search Jupiter has 63 known natural satellites. ... Jump to: navigation, search The Saturnian System (photographic montage) Saturn Rings and Satellites. ... Uranus has 27 known moons. ... Neptune has 13 known moons. ... Jump to: navigation, search Presentation of the solar system (not to scale) The solar system is the retinue of objects gravitationally bound to our Sun. ... Timeline of natural satellites in the Solar system by decade of discovery For comparison, discovery dates of Uranus, Neptune and Pluto are also included, as well as the first six asteroids. ... The naming of natural satellites has been the responsibility of the IAUs committee for Planetary System Nomenclature since 1973. ...

References

• http://cfa-www.harvard.edu/iau/special/08625.pdf
• http://www.boulder.swri.edu/plutonews/

External links

• Animation of the Plutonian system
• Hubble Spots Possible New Moons Around Pluto (NASA)
• Two More Moons Discovered Orbiting Pluto (SPACE.com)

Jump to: navigation, search Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Charon (shair-un or kair-un, Greek Χάρων) is the only known satellite of Pluto. ... Jump to: navigation, search Discovery images of S/2005 P 2. ... Jump to: navigation, search Discovery images of S/2005 P 1. ...