Galatea (moon)
From Wikipedia, the free encyclopedia
 Galatea as seen by Voyager 2 (smearing has caused excessive elongation) |
|
| Discovery | |
|---|---|
| Discovered by | Stephen P. Synnott[1] and Voyager Imaging Team |
| Discovered in | July 1989 |
| Orbital characteristics [2] | |
|
|
|
| Semi-major axis | 61 953 ± 1 km |
| Eccentricity | 0.00004 ± 0.00009 |
| Orbital period | 0.42874431 ± 0.00000001 d |
| Inclination | 0.052 ± 0.011° (to Neptune equator) 0.06° (to local Laplace plane) |
| Is a satellite of | Neptune |
| Physical characteristics | |
| Dimensions | 204×184×144 km (±~10 km) [3] |
| Mass | 2.12 ± 0.08 ×1018 kg [4] |
| Mean density | 0.75 ± 0.1 g/cm3 |
| Rotation period | assumed synchronous |
| Axial tilt | ~zero presumably |
| Albedo (geometric) | 0.08 [3] |
| Surface temp. | ~51 K mean (estimate) |
| Atmosphere | none |
- There is also an asteroid called 74 Galatea.
Galatea (gal'-ə-tee'-ə, IPA: [ˈɡæləˈtiə], Greek Γαλατεία), or Neptune VI, is the fourth closest inner satellite of Neptune. It is named after Galatea, one of the Nereids of Greek legend.
Galatea was discovered in late July, 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 4 [5] The discovery was announced (IAUC 4824) on August 2, 1989, but the text only talks of "10 frames taken over 5 days", giving a discovery date of sometime before July 28.
It is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit [6].
Galatea's orbit lies below Neptune's synchronous orbit radius, so it is slowly spiralling inward due to tidal decceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching.
Galatea appears to be a shepherd moon for the Adams ring that exists just outside Galatea's orbit. Resonances with Galatea in the ratio 42:43 are also considered the most likely mechanism for confining the unique ring arcs that exist in this ring [7]. Galatea's mass has been estimated based on the radial perturbations it induces on the ring [4].
[edit] References
- ^ Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/
- ^ R.A. Jacobson and W.M. Owen Jr. (2004). "The orbits of the inner Neptunian satellites from Voyager, Earthbased, and Hubble Space Telescope observations". Astronomical Journal 128: 1412.
- ^ a b E. Karkoschka (2003). "Sizes, shapes, and albedos of the inner satellites of Neptune". Icarus 162: 400.
- ^ a b C.C. Porco (1991). "An Explanation for Neptune's Ring Arcs". Science 253: 995.
- ^ discovery IAUC circular
- ^ D. Banfield and N. Murray (1992). "A dynamical history of the inner neptunian satellites". Icarus 99: 390.
- ^ F. Namouni and C. Porco (2002). "The confinement of Neptune's ring arcs by the moon Galatea". nature 417: 45.
[edit] See also
 |
|---|
| Naiad · Thalassa · Despina · Galatea · Larissa · Proteus Triton Nereid · S/2002 N 1 · S/2002 N 2 · S/2002 N 3 · Psamathe · S/2002 N 4 |
| See also: Neptune Trojans · Rings of Neptune |
