Mundilfari, or Saturn XXV, is a
natural satellite of
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 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
. It was discovered by
Brett J. Gladman, et al. in 2000, and given the temporary designation S/2000 S 9. Mundilfari is about 7 kilometers in diameter, and orbits Saturn at an average distance of 18,5903 Mm in 952.95 days, an
averaged eccentricity of 0.210,
and at an
inclination of 168.4° to the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.
Fr ...
in a
retrograde sense (compared to Saturn's orbit around the Sun).
Mundilfari may have formed from debris knocked off
Phoebe by large impacts at some point in the Solar System's history, but it is on an orbit sufficiently different from Phoebe that this may be difficult to reconcile. With a
spectral slope of −5.0%/100 , Mundilfari is the bluest of all the moons studied by Grav and Bauer (2007), slightly more so than Phoebe (−2.5%/100 nm) and about as blue as
Erriapus (+5.1%/100 nm) is red.
Its rotation period is hours, the second-fastest among all the irregular moons studied by ''
Cassini–Huygens'' after
Hati,
and it appears to be very elongated in shape.
It was named in August 2003 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 as the Nordic folklore of the modern period. The ...
, where
Mundilfari is the father of the goddess
Sól (Sun) and the god
Máni (Moon).
In 2023 announcements of 64 newly discovered irregular moons plus an additional 128 additional irregular moons in 2025 have suggested that Mundilfari is the largest remaining fragment of an entire sub-group of small retrograde irregular moons.
Notes
References
External links
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)
* https://phas.ubc.ca/2025-discovery-more-saturnian-moons March 11, 2025
{{DEFAULTSORT:Mundilfari (Moon)
Norse group
Moons of Saturn
Irregular satellites
Discoveries by Brett J. Gladman
Astronomical objects discovered in 2000
Moons with a retrograde orbit