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 ...

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; ...

. It was discovered by

Gladman Gladman is a surname. Notable people with the surname include: * Brett J. Gladman (born 1966), Canadian astronomer * Constance Helen Gladman (1922–1964), Australian Roman Catholic nun * Frederick John Gladman (1839–1884), Australian educator an ...

and colleagues in 2000, and given the temporary designation S/2000 S 7. Its name comes 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 peri ...

, 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 Phoebe or Phœbe may refer to: __NOTOC__ People and characters * Phoebe (given name), a list of people, mythological, biblical and fictional characters * Phoebe (Greek myth), several characters * Phoebe, an epithet of Artemis/ Diana and Selene/ L ...

. 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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

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 agai ...

(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- center, in geometry * Eccentricity (graph theory) of a ...

of 0.453. Like Ijiraq and Kiviuq, Thrymr's orbit overlaps strongly with

'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 ''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, including its ri ...

'' 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 Kiviuq 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 the ...

. 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 w ...

, 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 S/2004 S 7 is a natural satellite of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on 4 May 2005 from observations taken between 12 December 2004 and 8 March 2005. S/2004 S 7 is abou ...

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 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 ...

later decided to add the

nominative In grammar, the nominative case ( abbreviated ), subjective case, straight case or upright case is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or (in Latin and formal variants of ...

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