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Fenrir
Discovery
Discovery site	Subaru, Gemini; Jan T. Kleyna; Brian G. Marsden
Designations
Designation	Saturn XLI
Pronunciation	/ˈfɛnrɪər/ or /ˈfɛnrər/
Named after	Fenris Wolf
Alternative names	S/2004 S 16
Adjectives	Fenrian /ˈfɛnriən/
Orbital characteristics
Semi-major axis	22 454 000 km
Eccentricity	0.1363
Orbital period (sidereal)	1260.35 d (3.45 yr)
Mean anomaly	146.614°
Inclination	164.955°
Longitude of ascending node	330.95°
Argument of perihelion	120.264°
Satellite of	Saturn
Group	Norse group
Physical characteristics
Mean diameter	4 km
Albedo	0.06 (assumed)
Apparent magnitude	25.0
Absolute magnitude (H)	15.9

Fenrir /ˈfɛnrɪər/, or Saturn XLI (provisional designation S/2004 S 16), is a natural satellite of Saturn. 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 of 25,^[7] making it one of the faintest known moons in the Solar System, and was discovered using some of the largest telescopes in the world.^[1] It is even too dark to have been observed by the Cassini spacecraft when it was in orbit around Saturn, for which it never got brighter than approximately 17th apparent magnitude.^[8] Fenrir was named after Fenrisulfr, a giant wolf from Norse mythology, father of Hati and Skoll, son of Loki, destined to break its bonds for Ragnarök.

Fenrir is about 4 kilometres in diameter,^[7] and orbits Saturn at an average distance of 22,454 Mm in 1260 days, at an inclination of 163° to the ecliptic (143° to Saturn's equator) with an eccentricity 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.^[9]

Notes

^ The oblique stem of the name is Fenri, as in Fenrisulfr. The -r is the nominative case ending.

References

^ ^a ^b ^c Daniel W. E. Green (2005-05-04). "IAUC 8523: NEW Sats OF SATURN". International Astronomical Union.
^ "Fenrir". Dictionary.com Unabridged (Online). n.d.
^ Merriam-Webster's Encyclopedia of Literature (1995)
^ Daniel W. E. Green (2007-04-05). "IAUC 8826: Sats OF JUPITER, SATURN". International Astronomical Union.
^ Jacobson, R.A. (2007) SAT270, SAT271 (2009-04-03). "Planetary Satellite Mean Orbital Parameters". JPL/NASA. Retrieved 2009-07-30.{{cite web}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
^ Denk, Tilmann; Mottola, Stefano; Tosi, Frederico; Bottke, William F.; Hamilton, Douglas P. (2018). "The Irregular Satellites of Saturn" (PDF). In Schenk, P.M.; Clark, R.N.; Howett, C.J.A.; Verbiscer, A.J.; Waite, J.H. (eds.). Enceladus and the Icy Moons of Saturn. Space Science Series. Vol. 322. Tucson, AZ: The University of Arizona Press. pp. 409–434. Bibcode:2018eims.book..409D. doi:10.2458/azu_uapress_9780816537075-ch020. ISBN 9780816537075.
^ ^a ^b Scott S. Sheppard. "Saturn's Known Satellites". Carnegie Institution (Department of Terrestrial Magnetism). Retrieved 2009-07-30.
^ "Fenrir (S/2004 S 16) – Tilmann Denk". Retrieved 2024-02-10.
^ David C. Jewitt. "Twelve New Moons for Saturn - 2005 May 03". University of Hawaii (Institute for Astronomy). Archived from the original on September 18, 2009. Retrieved 2009-07-30.