Fenrir , or Saturn XLI (provisional designation S/2004 S 16), is a

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a deriv ...

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on May 4, 2005, from observations taken between December 13, 2004, and March 5, 2005. Fenrir has an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 25, making it one of the faintest known moons in the Solar System, and was discovered using some of the largest telescopes in the world. It is even too dark to have been observed by the Cassini spacecraft when it was in orbit around

, for which it never got brighter than approximately 17th apparent magnitude. Fenrir was named after Fenrir, a giant wolf from

Norse mythology Norse, Nordic, or Scandinavian mythology, is the body of myths belonging to the North Germanic peoples, stemming from Old Norse religion and continuing after the Christianization of Scandinavia as the Nordic folklore of the modern period. The ...

, father of Hati and Skoll, son of

Loki Loki is a Æsir, god in Norse mythology. He is the son of Fárbauti (a jötunn) and Laufey (mythology), Laufey (a goddess), and the brother of Helblindi and Býleistr. Loki is married to the goddess Sigyn and they have two sons, Narfi (son of Lo ...

, destined to break its bonds for

Ragnarök In Norse mythology, (also Ragnarok; or ; ) is a foretold series of impending events, including a great battle in which numerous great Norse mythological figures will perish (including the Æsir, gods Odin, Thor, Týr, Freyr, Heimdall, a ...

. Fenrir is about 4 kilometres in diameter, and orbits Saturn at an average distance of 22,454 Mm in 1260 days, at an inclination of 163° to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

(143° to Saturn's equator) with an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.136. The Fenrian orbit is retrograde: it orbits Saturn in a direction opposite to the planet's spin, suggesting that this irregular moon was captured by Saturn.

Notes

References

External links

Saturn's Known Satellites
(by Scott S. Sheppard)
MPEC 2005-J13: ''Twelve New Satellites of Saturn''
May 3, 2005 (discovery and initial ephemeris) {{Moons of Saturn, state=uncollapsed Moons of Saturn Norse group Irregular satellites Discoveries by Scott S. Sheppard Astronomical objects discovered in 2005 Moons with a retrograde orbit