Galatea (moon)

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Galatea

Galatea as seen by Voyager 2 (smearing has caused excessive elongation)
Discovery
Discovered by	Voyager Imaging Team
Discovered in	July 1989
Orbital characteristics
Semi-major axis	61 953 ± 1 km
Eccentricity	0.00004 ± 0.00009
Orbital period	0.42874431 ± 0.00000001 d
Inclination	0.59 ± 0.01° (to Neptune equator) 0.06° (to local Laplace plane)
Is a satellite of	Neptune
Physical characteristics
Dimensions
Mass
Mean density	0.75 ± 0.1 g/cm3
Rotation period	assumed synchronous
Axial tilt	~zero presumably
Albedo (geometric)	0.08
Surface temp.	~51 K mean (estimate)
Atmosphere	none

There is also an asteroid called 74 Galatea.

A simulated view of Galatea orbiting Neptune

Galatea (gal'-ə-tee'-ə, IPA /ˈɡæləˈtiə/, Greek Γαλατεία), or Neptune VI, is the fourth known moon 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 [discovery IAUC circular] 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 .

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 is ring . Galatea's mass has been estimated based on the radial perturbations it induces on the ring .

References