Fornjot or Saturn XLII is the third outermost

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'' ...

of Saturn (after S/2004 S 34 and S/2004 S 26). Its discovery was announced by

Scott S. Sheppard Scott Sander Sheppard (born 1977) is an American astronomer and a discoverer of numerous moons, comets and minor planets in the outer Solar System. He is an astronomer in the Department of Terrestrial Magnetism at the Carnegie Institution for Scie ...

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 4 May 2005 from observations taken between 12 December 2004, and 11 March 2005. It had the largest semi-major axis among all the known moons of Saturn until the recovery of Saturn LVIII in 2019. It is about 6 kilometres in diameter, and it orbits Saturn at an average distance of 23,609 Mm in 1491 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 Eart ...

of 168° 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 ...

(160° to Saturn's equator) in a retrograde direction and 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 0.186. It is ambiguous whether the rotation period is 6.9 or hours, but it is known to show very little variation in brightness and is probably very round in shape. It was also the faintest moon that was measured by '' Cassini–Huygens''. Fornjot was named after

Fornjót Fornjót (Old Norse: ''Fornjótr'') is a jötunn in Norse mythology, and the father of Hlér ('sea'), Logi ('fire') and Kári ('wind'). It is also the name of a legendary king of " Finnland and Kvenland". The principal study of this figure i ...

, a giant in Norse mythology.

References

Institute for Astronomy Saturn Satellite Data

May 4, 2005 (discovery)

May 3, 2005 (discovery and ephemeris)

April 5, 2007 (naming the moon) {{DEFAULTSORT:Fornjot (Moon) Norse group Moons of Saturn Irregular satellites Discoveries by Scott S. Sheppard Astronomical objects discovered in 2005 Moons with a retrograde orbit