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 often colloquially referred to as ''moons'' ...

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 nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

. Its discovery was announced by Scott S. Sheppard,

David C. Jewitt David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pl ...

Jan Kleyna Jan T. Kleyna is a postdoctoral astronomy researcher at the University of Hawai'i A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities t ...

, and

Brian G. Marsden Brian Geoffrey Marsden (5 August 1937 – 18 November 2010) was a British astronomer and the longtime director of the Minor Planet Center (MPC) at the Center for Astrophysics Harvard & Smithsonian (director emeritus from 2006 to 2010). ...

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 brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

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 darkFenrir
Tilmann Denk to have been observed by the

Cassini spacecraft Cassini may refer to: People * Cassini (surname) * Oleg Cassini (1913-2006), American fashion designer :Cassini family: * Giovanni Domenico Cassini (1625–1712), Italian mathematician, astronomer, engineer, and astrologer * Jacques Cassini (1 ...

when it was in orbit around

, for which it never got brighter than approximately 17th

. Fenrir was named after

Fenrisulfr Fenrir (Old Norse: ; "fen-dweller")Orchard (1997:42). or Fenrisúlfr (O.N.: ; "Fenrir's wolf", often translated "Fenris-wolf"),Simek (2007:81). also referred to as Hróðvitnir (O.N.: ; "fame-wolf")Simek (2007:160). and Vánagandr (O.N.: ; " ...

, 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, and into the Nordic folklore of the modern per ...

, father of Hati and Skoll, son of

Loki Loki is a god in Norse mythology. According to some sources, Loki is the son of Fárbauti (a jötunn) and Laufey (mentioned as a goddess), and the brother of Helblindi and Býleistr. Loki is married to Sigyn and they have two sons, Narfi ...

, destined to break its bonds for

Ragnarök In Norse mythology, (; non, wikt:ragnarǫk, Ragnarǫk) is a series of events, including a great battle, foretelling the death of numerous great figures (including the Æsir, gods Odin, Thor, Týr, Freyr, Heimdallr, and Loki), natural disast ...

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

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Ea ...

of 163° to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

(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 In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular ...

was captured by Saturn.

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