|Discovered by||Carolyn Porco|
|Discovery date||March 3, 2009|
|Cassini Imaging Science Team|
|Epoch JD 2454467.00075444 TDB|
|493.665±0.004 km 167|
|0.80812 d |
|(linear drift) ±0.007°/day 445.475|
|Dimensions||(±0.10)×( 1.40±0.12)×( 0.50±0.16) km 0.40|
Aegaeon (// ee-JEE-ən; or as Greek Αιγαίων), also Saturn LIII (provisional designation S/2008 S 1), is a natural satellite of Saturn. It is thought to be similarly smooth as Methone. It orbits between Janus and Mimas within Saturn's G Ring.
Discovery and naming
Images of Aegaeon were taken by Cassini on 15 August 2008, and its discovery was announced on 3 March 2009 by Carolyn Porco of the Cassini Imaging Science Team using the provisional designation S/2008 S 1.
Aegaeon orbits within the bright segment of Saturn's G Ring, and is probably a major source of the ring. Debris knocked off Aegaeon forms a bright arc near the inner edge, which in turn spreads to form the rest of the ring. Aegaeon orbits in a 7:6 corotation eccentricity resonance with Mimas, which causes an approximately 4-year oscillation of about 4 km in its semi-major axis, and a corresponding oscillation of a few degrees in its mean longitude. It orbits Saturn at an average distance of 167,500 km in 0.80812 days, at an inclination of 0.001° to Saturn's equator, with an eccentricity of 0.0002.
Aegaeon is the smallest known moon of Saturn and has a highly elongated shape, measuring 1.4x0.5x0.4 km in size. Measurements of its mass, based on its interaction with the dust particles that make up the G ring arc the moon is embedded in, suggest a density similar to that of water ice. Aegaeon has the lowest albedo, below 0.15, of any Saturnian moon inward of Titan. This might be due to either darker meteoric material making up the dust in the G ring or due to Aegaeon having been disrupted, stripping away its ice-rich surface and leaving the rocky inner core behind.
The Cassini spacecraft has performed four flybys of Aegaeon closer than 20,000 km, though only one has occurred since it was discovered in 2008. The closest of these pre-discovery encounters took place on 5 September 2005 at a distance of 8,517 km. An encounter on 27 January 2010 at a distance 13,306 km allowed Cassini to acquire its highest resolution images of Aegaeon to-date. On 19 December 2015, Cassini was unable to acquire any images from a planned close flyby.
- IAU Circular No. 9023
- Thomas, P. C.; Burns, J. A.; Tiscareno, M. S.; Hedman, M. M.; et al. (2013). "Saturn's Mysterious Arc-Embedded Moons: Recycled Fluff?" (PDF). 44th Lunar and Planetary Science Conference. p. 1598. Retrieved 2013-05-21.
- Hedman, M.M.; Cooper, N.J.; Murray, C.D.; Beurle, K.; Evans, M.W.; Tiscareno, M.S.; Burns, J.A. (May 2010). "Aegaeon (Saturn LIII), a G-ring object". Icarus. 207 (1): 433–447. arXiv:0911.0171. Bibcode:2010Icar..207..433H. doi:10.1016/j.icarus.2009.10.024.
- Battersby, S. (2013-05-17). "Saturn's egg moon Methone is made of fluff". www.newscientist.com. New Scientist. Retrieved 2013-05-21.
- Jennifer Blue, Saturnian Satellite Named Aegaeon, USGS Astrogeology Hot Topics, 5 May 2009
- Petite Moon, CICLOPS, 29 May 2009
- Thomas, P.C.; Burns, J.A.; Hedman, M.; Helfenstein, P.; Morrison, S.; Tiscareno, M.S.; Veverka, J. (2013). "The inner small satellites of Saturn: A variety of worlds" (PDF). Icarus. 226 (1): 999–1019. Bibcode:2013Icar..226..999T. doi:10.1016/j.icarus.2013.07.022. Retrieved 2 December 2015.
- Hedman, M.M.; Burns, J.A.; Thomas, P.C.; Tiscareno, M.S.; Evans, M.W. (2011). Physical Properties of the small moon Aegaeon (Saturn LIII) (PDF). European Planetary Space Conference. Icarus. 6. Retrieved 2 December 2015.
- Planetary Society Cassini Timeline