page_title: Satellite system (astronomy)
section_title: Notable satellite systems
hierarchical_section_title: Satellite system (astronomy) / Notable satellite systems
caption_attribution_description: English: This image, taken by NASA's Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The newly discovered small moon, Styx (initially designated P5), is the innermost of the moons found by Hubble over the past seven years. The diagram shows that Styx is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system. Though Charon (discovered in 1978) is an even closer moon to Pluto, some astronomers consider the Pluto-Charon pair a "double planet" because Charon's mass is 12 percent of Pluto's mass (by comparison, our Moon is 1.2 percent Earth's mass). This image was taken with Hubble's Wide Field Camera 3 on July 7. Other observations that collectively show the moon's orbital motion were taken on June 26, 27, and 29, 2012 and July 9, 2012. The new data will help scientists in their planning for the July 2015 flyby of Pluto by NASA's New Horizons spacecraft. The original NASA image has been modified by replacing "P4" and "P5" with newer designations "Kerberos" and "Styx", respectively.
context_page_description: A satellite system is a set of gravitationally bound objects in orbit around a planetary mass object or minor planet, or its barycenter. Generally speaking, it is a set of natural satellites, although such systems may also consist of bodies such as circumplanetary disks, ring systems, moonlets, minor-planet moons and artificial satellites any of which may themselves have satellite systems of their own. Some bodies also possess quasi-satellites that have orbits gravitationally influenced by their primary, but are generally not considered to be part of a satellite system. Satellite systems can have complex interactions including magnetic, tidal, atmospheric and orbital interactions such as orbital resonances and libration. Individually major satellite objects are designated in Roman numerals. Satellite systems are referred to either by the possessive adjectives of their primary, or less commonly by the name of their primary. Where only one satellite is known, or it is a binary orbiting a common centre of gravity, it may be referred to using the hyphenated names of the primary and major satellite.
context_section_description: Known satellite systems of the Solar System consisting of multiple objects or around planetary mass objects, in order of perihelion:
caption: The Pluto-Charon system (with orbital paths illustrated): The binaries Pluto and Charon orbited by Nix, Hydra, Kerberos, and Styx, taken by the Hubble Space Telescope in July 2012
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