Skip to main content
Select Source:

Janus (in astronomy)

Janus (jā´nəs), 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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus (in astronomy)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus (in astronomy)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/janus-astronomy

"Janus (in astronomy)." The Columbia Encyclopedia, 6th ed.. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/janus-astronomy

Janus

Janus

Janus was the Roman god of beginnings, gates, and doorways. He was associated with the start of day and the first month of the year, called January after him. The Romans mentioned Janus first when including a list of gods in their prayers, and they named the Janiculum, one of the seven hills of Rome, in his honor.

Like a doorway that can be entered from two directions, Janus was usually pictured with two faces, one looking forward and one looking back. The temple to Janus in the Roman Forum had two sets of doors facing east and west. These doors were open during a war and closed in periods of peace.

Janus appears in one myth as the defender of an important Roman gateway When the city was under attack by a tribe known as the Sabines, Janus flooded the gate with a hot spring to prevent the invaders from entering the city. In another story, Janus used his two faces while pursuing a lover. The goddess Cardea was known for leading her admirers to a cave and then running away. When Janus accompanied her to the cave, he saw with the face in the back of his head that she was turning to leave and caught hold of her before she could escape.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus." Myths and Legends of the World. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus." Myths and Legends of the World. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/humanities/news-wires-white-papers-and-books/janus

"Janus." Myths and Legends of the World. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/news-wires-white-papers-and-books/janus

Janus (in Roman religion)

Janus (jā´nəs), 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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus (in Roman religion)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus (in Roman religion)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/janus-roman-religion

"Janus (in Roman religion)." The Columbia Encyclopedia, 6th ed.. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/janus-roman-religion

Janus

Janus in Roman mythology, an ancient Italian deity, guardian of doorways and gates and protector of the state in time of war; he is usually represented with two faces, so that he looks both forwards and backwards. In ancient Rome the doors of the shrine of Janus in the Forum were closed in times of peace; according to Livy between the time of Numa and his own day, this happened only twice, once after the First Punic War (241 bc) and after Octavian's victory at Actium (31 bc).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus." The Oxford Dictionary of Phrase and Fable. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus." The Oxford Dictionary of Phrase and Fable. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/janus

"Janus." The Oxford Dictionary of Phrase and Fable. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/janus

Janus

Janus (Saturn X) One of the lesser satellites of Saturn, with a radius measuring 99.3 × 95.6 × 75.6 km; mass 0.0198 × 1020 kg; mean density 650 kg/m3; visual albedo 0.8. It was discovered in 1966 by A. Dolfus, Gerard Kuiper, J. Fountain, and S. Larsen.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus." A Dictionary of Earth Sciences. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus." A Dictionary of Earth Sciences. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/janus

"Janus." A Dictionary of Earth Sciences. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/janus

Janus

Janus •pandanus •badness, madness, sadness •Magnus • aptness •fatness, patness •redness • wetness •anus, Coriolanus, heinous, Janus, Punta Arenas, Silvanusgenus, intravenous, Maecenas, Malvinas, Salinas, venous, Venus •Cygnus • proteinous • ruinous •libidinous •multitudinous, platitudinous, pulchritudinous, vicissitudinous •cartilaginous, farraginous, oleaginous •fuliginous, indigenous, oxygenous, polygynous, rubiginous, vertiginous •androgynous, autogenous, endogenous, erogenous, exogenous, homogenous, hydrogenous, misogynous •ferruginous • ominous •bituminous, leguminous, luminous, numinous, voluminous •conterminous, coterminous, terminus, verminous •larcenous • gelatinous • cretinous •mountainous •glutinous, mutinous •resinous •Aquinas, Delphinus, echinus, Linus, Longinus, minus, Plotinus, sinus, vinous •oddness • wanness • hotness •Faunus, rawness •Kaunas •bonus, Cronus, Jonas, lowness, onus, Tithonus •oldness •newness, twoness •fulness •alumnus, rumness •oneness • Oceanus • Eridanus •diaphanous • polyphonous •cacophonous, homophonous •porcellanous • villainous •membranous • tyrannous •synchronous • Uranus • tetanus •monotonous • gluttonous •cavernous, ravenous •treasonous • poisonous • Avernus

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Janus." Oxford Dictionary of Rhymes. . Encyclopedia.com. 14 Dec. 2017 <http://www.encyclopedia.com>.

"Janus." Oxford Dictionary of Rhymes. . Encyclopedia.com. (December 14, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/janus-0

"Janus." Oxford Dictionary of Rhymes. . Retrieved December 14, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/janus-0