Thalassa (moon)

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Thalassa
Naiad Voyager.png
Naiad or Thalassa as seen by Voyager 2 (elongation is due to smearing)
Discovery
Discovered by Richard J. Terrile[1] and Voyager Imaging Team
Discovery date September 1989
Orbital characteristics[2]
Epoch 18 August 1989
50 075 ± 1 km
Eccentricity 0.0002 ± 0.0002
0.31148444 ± 0.00000006 d
Inclination
  • 0.21 ± 0.02° (to Neptune equator)
  • 0.21° (to local Laplace plane)
Satellite of Neptune
Physical characteristics
Dimensions 108×100×52 km[3][4]
Mean radius
 41 ± 3 km[5]
Volume ~2.9×105km³
Mass ~3.5×1017 kg
(based on assumed density)
Mean density
 ~1.2 g/cm³ (estimate)[5]
synchronous
zero
Albedo 0.09[3][5]
Temperature ~51 K mean (estimate)
23.3[5]
A simulated view of Thalassa orbiting Neptune.

Thalassa (/θəˈlæsə/ thə-LASS-ə; Greek: Θάλασσα), also known as Neptune IV, is the second innermost satellite of Neptune. Thalassa was named after sea goddess Thalassa, a daughter of Aether and Hemera from Greek mythology. "Thalassa" is also the Greek word for "sea".

A Voyager 2 image of Thalassa (1989 N5), Naiad (1989 N6) and Despina (1989 N3)

Thalassa was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 5.[6] The discovery was announced (IAUC 4867) on September 29, 1989, but the text only talks of "25 frames taken over 11 days", giving a discovery date of sometime before September 18. The name was given on 16 September 1991.[7]

Thalassa 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.[8] Unusually for irregular bodies, it appears to be roughly disk-shaped.

Since the Thalassian orbit is below Neptune's synchronous orbit radius, it is slowly spiralling inward due to tidal deceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching. Relatively soon after, the spreading debris may impinge upon Despina's orbit.

References

  1. ↑ Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 5.2 5.3 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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