Janus (redirected from Janus (disambiguation))

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.

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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.

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Janus

The god Janus, beardless, Roman coin; in the Bibliothèque Nationale, Paris

(credit: Larousse)

Roman god of doorways and archways, after whom the month of January is named. Often depicted as a double-faced head, he was a deity of beginnings. The worship of Janus dated back to the earliest years of Rome, and the city had many freestanding ceremonial gateways called jani, used for symbolically auspicious entrances or exits. The most famous was the Janus Geminus, whose double doors were left open in time of war and closed when Rome was at peace. The festival of Janus, the Agonium, took place on January 9.

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Janus [′jā·nəs]

(astronomy)

A satellite of Saturn which orbits at a mean distance of 151,000 kilometers (94,000 miles) and has an irregular shape with an average diameter of 190 kilometers (120 miles).

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bifrons

bifrons

Having two fronts or faces looking in opposite directions, as a double herm.

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1.		Janus - Distributed language with an ask/tell constraint system. qdjanus is a Janus-to-Prolog compiler for Sicstus Prolog and jc is compiles to C. ["Janus: A Step Towards Distributed Constraint Programming", V. Saraswat <saraswat@parc.xerox.com> et al in Logic Programming: Proc 1990 North Am Conf, S. Debray et al eds, MIT Press 1990]. ["Programming in Janus", Saraswat, Kahn, and Levy].
2.		Janus - W.M. Waite, U Colorado. Intermediate language, claimed as an implementation of UNCOL. Used on CDC 6600. ["Experience with the Universal Intermediate Language Janus", B.K. Haddon et al, Soft Prac & Exp 8(5):601- 616 (Sep 1978)].