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Prometheus (moon)

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Prometheus 12-26-09b.jpg
Prometheus image from Cassini (December 26, 2009)
Discovered byCollins, Voyager 1
Discovery dateOctober, 1980
Saturn XVI
Named after
Προμηθεύς Promētheys
AdjectivesPromethean, -ian /prəˈmθən/[2]
Orbital characteristics[3]
Epoch 31 December 2003 (JD 2453005.5)
139380±10 km
0.612990038 d
Inclination0.008°±0.004° to Saturn's equator
Satellite ofSaturn
GroupInner shepherd moon of the F Ring
Physical characteristics
Dimensions135.6 × 79.4 × 59.4 km [4]
Mean radius
43.1±2.7 km[4]
Volume≈ 340000 km3[4]
Mass(1.595±0.015)×1017 kg[4]
Mean density
0.48±0.09 g/cm³[4]
0.0013–0.0058 m/s²[4]
≈ 0.019 km/s
Temperature≈ 74 K

Prometheus /prəˈmθəs/ is an inner satellite of Saturn. It was discovered in 1980 (in 24 October) from photos taken by the Voyager 1 probe, and was provisionally designated S/1980 S 27.[5]

In late 1985 it was officially named after Prometheus, a Titan in Greek mythology.[6] It is also designated Saturn XVI.[7]

Prometheus is extremely elongated, measuring approximately 136 km × 79 km × 59 km (85 mi × 49 mi × 37 mi). It has several ridges and valleys and a number of impact craters of about 20 km (12 mi) diameter are visible, but it is less cratered than nearby Pandora, Epimetheus, and Janus. From its very low density and relatively high albedo, it is likely that Prometheus is a very porous icy body. There is much uncertainty in these values, however, and so this remains to be confirmed.

Interactions with F Ring and other moons[edit]

Prometheus is a shepherd satellite for the inner edge of Saturn's narrow F Ring. Pandora orbits just outside the F Ring, and has traditionally been viewed as an outer shepherd of the ring; however, recent studies indicate that only Prometheus contributes to the confinement of the ring.[8][9]

Images from the Cassini probe show that the Promethean gravitational field creates kinks and knots in the F Ring as it 'steals' material from it. The orbit of Prometheus appears to be chaotic, due to a series of four 121:118 mean-motion resonances with Pandora.[10] The most appreciable changes in their orbits occur approximately every 6.2 years,[3] when the periapsis of Pandora lines up with the apoapsis of Prometheus, when they approach to within approximately 1400 km. Prometheus is itself a significant perturber of Atlas, with which it is in a 53:54 mean-longitude resonance.[3]

Selected images[edit]




  1. ^ "Prometheus". Lexico UK Dictionary. Oxford University Press.
  2. ^ "Promethean". Lexico UK Dictionary. Oxford University Press.
  3. ^ a b c Spitale Jacobson et al. 2006.
  4. ^ a b c d e f Thomas 2010.
  5. ^ IAUC 3532.
  6. ^ IAUC 4157.
  7. ^ USGS: Planet and Satellite Names and Discoverers.
  8. ^ Lakdawalla, E. (2014-07-05). "On the masses and motions of mini-moons: Pandora's not a "shepherd," but Prometheus still is". Planetary Society. Retrieved 2015-04-17.
  9. ^ Cuzzi, J. N.; Whizin, A. D.; Hogan, R. C.; Dobrovolskis, A. R.; Dones, L.; Showalter, M. R.; Colwell, J. E.; Scargle, J. D. (April 2014). "Saturn's F Ring core: Calm in the midst of chaos". Icarus. 232: 157–175. Bibcode:2014Icar..232..157C. doi:10.1016/j.icarus.2013.12.027. ISSN 0019-1035.
  10. ^ Renner et al. 2005.


External links[edit]

Media related to Prometheus (moon) at Wikimedia Commons