Bestla /ˈbɛstlə/ or Saturn XXXIX is a retrograde irregular moon 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 13 December 2004 and 5 March 2005.
Discovery | |
---|---|
Discovered by | Scott S. Sheppard David C. Jewitt Jan T. Kleyna Brian G. Marsden |
Discovery date | 2004 |
Designations | |
Designation | Saturn XXXIX |
Pronunciation | /ˈbɛstlə/ |
Named after | Bestla |
S/2004 S 18 | |
Orbital characteristics[1] | |
20337900 km | |
Eccentricity | 0.461 |
−1087.46 days | |
Inclination | 136.3° |
Satellite of | Saturn |
Group | Norse group |
Physical characteristics | |
Dimensions | 15.56 × 7 × 5.98 km (modeled)[2] |
Mean diameter | 7+50% −30% km[3] |
−14.6238±0.0001 h[3] | |
Pole ecliptic latitude | 85°+5° −15°[4][a] |
Albedo | 0.06 (assumed)[3] |
23.8[4] | |
14.6[4] | |
Bestla is about 7 kilometres in diameter, and orbits Saturn at an average distance of 20,337,900 km in 1087 days, at an inclination of 136° to the ecliptic, in a retrograde direction and with an eccentricity of 0.461.[1] Early observations from 2005 suggested that Bestla had a very high eccentricity of 0.77.[5] Like many of the outer irregular moons of the giant planets, Bestla's eccentricity may vary as a result of the Kozai mechanism. Bestla rotates in a retrograde direction and makes a full rotation every 14.6238±0.0001 hours.[3] Like Kiviuq, it is likely to be a contact binary or binary object, as its light curve has strong variation in brightness and a plateau-like maximum not seen in the other irregulars.[4]
This moon was named in April 2007 after Bestla, a frost giantess from Norse mythology, who is a mother of Odin.