Janus, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn X (or S10), Janus is an irregularly shaped (nonspherical) body measuring about 122 mi (196 km) by 119 mi (192 km) by 93 mi (150 km); it orbits Saturn at a mean distance of 94,120 mi (151,472 km), and has equal orbital and rotational periods of 0.6945 earth days. The French astronomer Audouin Dollfus is credited with the discovery of Janus in 1966. However, in 1978, the American astronomers Stephen M. Larson and John W. Fountain determined that there were two moons orbiting Saturn at a distance of about 94,000 mi, and it was not until 1980 that the Voyager 1 space probe provided sufficient data to enable Janus to be distinguished from Epimetheus; today it is difficult to say which one Dollfus really discovered. Janus and Epimetheus are co-orbital, that is, they share the same average orbit; about every fourth year—at closest approach—the lower, faster satellite overtakes the other, they exchange angular momentum, and the lower one is boosted into a higher orbit while the higher one drops to the lower orbit. The two moons may have formed from the disruption of a single satellite early in the formation of Saturn's satellite system. Janus's surface is extensively cratered, with several larger than 18 mi (30 km); however, there are few linear features.
Janus, in Roman religion, god of beginnings. He was one of the principal Roman gods, the custodian of the universe. The first hour of the day, the first day of the month, the first month of the year (which bears his name) were sacred to him. His chief function was as guardian deity of gates and doors. The gates of his temple in the Roman Forum were closed in time of peace and opened in time of war. Janus was usually represented with two bearded heads placed back to back so that he might look in two directions at the same time. His principal festival was celebrated on the first day of the year.
Janus may refer to:

  • Janus (mythology), the two-faced Roman god of gates, doors, doorways, beginnings, and endings.
  • Janus (moon), a moon of Saturn.
  • Janus Patera, a shallow volcanic crater on Io, a moon of Jupiter.
  • Janus (simulation), a military combat simulation first developed in the late 1970s by the Lawrence Livermore National Laboratory's Combat Simulation Laboratory.
  • Society of Janus, a San Francisco based BDSM education and support group.
  • Janus Capital Group, an investment company based in Denver, Colorado.
  • Zündapp Janus, a bubble car model by Zündapp.
  • a Janus word, or auto-antonym: a word with two opposite meanings.
  • Janus (TV series), A television series created by the Australian Broadcasting Commission with two story lines: the criminal family being prosecuted and the police/judicial process.
  • Schempp-Hirth Janus, a two-seater glider.
  • HMS Janus, a name used by British naval ships.



Film and music

  • Janus Films, an American film distribution company.
  • Janus Records, a record label.
  • Janus (band), an orchestral darkwave group.
  • Janus, the criminal organization in the James Bond movie GoldenEye.
  • The Janus Project, a taboo cloning project in the movie Judge Dredd.
  • "Janus", a song from the album Out and About with the Gone Jackals by hard rock group The Gone Jackals.
  • "Janus" appears on the CD Inner Journeys: Myth + Legends by Cusco

Literature and comics

  • Janus: A Summing Up, a book by Arthur Koestler.
  • Janus (comics), a superhero in the DC Comics universe.
  • Janus (Marvel Comics), a superhero in the Marvel Comics universe and an enemy of Marvel Comics' Dracula.
  • The Janus Directive, a DC Comics crossover.
  • Janus (Stargate), an "Ancient" scientist in the TV series Stargate Atlantis and Stargate SG-1.
  • Janus (Angels and Demons), the antagonist in the novel Angels and Demons.
  • Janus, a French poetry magazine published in Paris by Elliott Stein from 1950 to 1961.
  • Janus Publishing, a British publishing company known for publishing the work of previously unpublished authors.
  • Janus, a short story by Ann Beattie.


Games and gaming



  • Janus-faced molecule, used to describe a molecule whose effects on organisms can vary between beneficial and toxic.
  • Janus Experiments, a series of experiments on radio-sensitivity in mice and dogs.

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