Thrymr , or Saturn XXX, 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'' ...

of Saturn. It was discovered by Gladman and colleagues in 2000, and given the temporary designation S/2000 S 7. Its name comes from Norse mythology, where Thrymr is a Jotun. Thrymr is about 7 kilometres in diameter, and orbits Saturn at an average distance of 20,810 Mm in 1120.809 days. It may have formed from debris knocked off Phoebe. The Thrymian orbit is retrograde, 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 175° 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 ...

(151° to Saturn's equator) 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 0.453. Like Ijiraq and

Kiviuq Kiviuq (also spelled "Qiviuq", "Kiviok" and other variants) is a legendary hero of the epic stories of the Inuit of the Arctic regions of northern Canada, Alaska and Greenland. Kiviuq is an eternal Inuit wanderer. Spirits, giants, cannibals, bea ...

, Thrymr's orbit overlaps strongly with Phoebe's such that it is likely to collide with it in the future. Its rotation period is hours, the slowest among the retrograde moons measured by '' Cassini–Huygens'' and the second-slowest after Tarqeq. Having two maxima and two minima in its

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

, it may therefore be a

contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overconta ...

, although this is less likely than for

and

Bestla Bestla (Old Norse: ) is a jötunn in Norse mythology, and the mother of the gods Odin, Vili and Vé (by way of Borr). She is also the sister of an unnamed man who assisted Odin, and the daughter (or granddaughter depending on the source) of th ...

. The surface of Thrymr is gray in color and similar to those of Suttungr and

Mundilfari In Norse mythology Mundilfari (Old Norse: ; rendered variously ''Mundilfari'', ''Mundilföri'' and ''Mundilfœri'') (Old Norse, possibly "the one moving according to particular times"Simek (2007:222).) is the father of Sól, goddess associated ...

, suggesting a common origin as fragments knocked off of Phoebe early in the Solar System's history. In particular, it may be part of the same dynamical family as Suttungr, though S/2004 S 7 is probably more closely related. Its name was announced in its oblique form Thrym i
IAU Circular 8177
However, the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

Working Group on Planetary System Nomenclature later decided to add the nominative suffix ''-r'' to the root ''Thrym''.

References

IAUC 7538: ''S/2000 S 7, S/2000 S 8, S/2000 S 9''
December 7, 2000 (discovery)

December 19, 2000 (discovery and ephemeris)

August 8, 2003 (naming the moon ''Thrym'')

January 21, 2005 (correcting the name)

References

Further reading