Prometheus (moon)

Infobox Planet
name = Prometheus


caption = Prometheus, as imaged by Voyager 2 on August 25, 1981
bgcolour = #a0ffa0
discovery = yes
discoverer = Collins, Voyager 1
discovered = October, 1980
orbit_ref = cite journal | author= Spitale, J. N.; "et al."| title= "The orbits of Saturn's small satellites derived from combined historic and "Cassini" imaging observations"| journal= The Astronomical Journal| year= 2006| volume= 132 | issue=2 | pages= 692–710 | url=http://www.iop.org/EJ/article/1538-3881/132/2/692/205235.html | doi= 10.1086/505206]
epoch = 31 December 2003 (JD 2453005.5
semimajor = 139,380 ± 10 km
eccentricity = 0.0022
period = 0.612990038 d
inclination = 0.008 ± 0.004° to Saturn's equator
satellite_of = Saturn
physical_characteristics = yes
dimensions = 119×87×61 km cite journal | author= Porco, C. C.; "et al."| title= "Physical Characteristics and Possible Accretionary Origins for Saturn's Small Satellites"| journal= Bulletin of the American Astronomical Society| year= 2006| volume= 37| pages= 768| url=http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2289.pdf]
mean_radius = 43 ± 2 km
surface_area = ~23,000 km²
volume = ~340,000 km³
mass = 1.566 ± 0.019 e|17 kg
density = 0.47 ± 0.07 g/cm³
surface_grav = ~0.003 m/s²
escape_velocity = ~0.019 km/s
rotation = synchronous
axial_tilt = zero
albedo = 0.6
single_temperature = ~74 K

Prometheus (pronEng|proʊˈmiːθiəs respell|proh|MEE|thee-əs, IPAlink-en|proʊˈmiːθjuːs respell|proh|MEE|thyoos, or as in Greek "Προμηθέας)" is an inner satellite of Saturn. It was discovered in 1980 (some time before October 25) from photos taken by the "Voyager 1" probe, and was provisionally designated nowrap|S/1980 S 27. [http://cfa-www.harvard.edu/iauc/03500/03532.html IAUC 3532: "Satellites of Saturn"] 1980 October 31 (discovery)]

In late 1985 it was officially named after Prometheus, a Titan in Greek mythology. [http://cfa-www.harvard.edu/iauc/04100/04157.html IAUC 4157: "Satellites of Saturn and Pluto"] 1986 January 3 (naming the moon)] It is also designated nowrap|Saturn XVI.cite web
title = Planet and Satellite Names and Discoverers
work = Gazetteer of Planetary Nomenclature
publisher = USGS Astrogeology
date = July 21, 2006
url = http://planetarynames.wr.usgs.gov/append7.html
accessdate = 2006-08-07 ]

This small moon is extremely elongated, measuring about 119 by 87 by 61 km. It has several ridges and valleys and a number of impact craters of about 20 km diameter are visible, but it is less cratered than nearby Pandora, Epimetheus and Janus. From its very low density and relatively high albedo, it seems likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.Fact|date=February 2007

Prometheus acts as a shepherd satellite for the inner edge of Saturn's F Ring. Recent images from the Cassini probe show that the Promethean gravitational field creates kinks and knots in the F Ring as the moon 'steals' material from it. The orbit of Prometheus appears to be chaotic, as a consequence of a mean motion resonance with Pandora. The most appreciable changes in their orbits occur approximately every 6.2 years, when the periapsis of Pandora lines up with the apoapsis of Prometheus and the moons approach to within about 1400 km. Prometheus is itsef a significant perturber of Atlas.

There is also an asteroid called 1809 Prometheus.

Image gallery

References

External links

* [http://saturn.jpl.nasa.gov/multimedia/videos/video-details.cfm?videoID=163 Prometheus collides with the F Ring] , pulls away a streamer, and creates another channel
* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Prometheus Prometheus Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.planetary.org/explore/topics/saturn/prometheus.html The Planetary Society: Prometheus]