Despina (moon)
Despina /dɛˈspaɪnə/, also known as Neptune V, is the third-closest inner moon of Neptune. It is named after Greek mythological character Despoina, a nymph who was a daughter of Poseidon and Demeter.
Discovery
Despina was discovered in late July 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 3.[7] The discovery was announced (IAUC 4824) on 2 August 1989, and mentions "10 frames taken over 5 days", implying a discovery date of sometime before July 28. The name was given on 16 September 1991.[8]
Physical characteristics
Despina's diameter is approximately 150 kilometres (93 mi).[4] Despina 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 disrupted by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.[9]
Orbit
Despina's orbit lies close to but outside of the orbit of Thalassa and just inside the Le Verrier ring and acts as its shepherd moon.[10] As it is also 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.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Simulated_view_of_Despina.jpg/220px-Simulated_view_of_Despina.jpg)
Notes
- ^ Volume derived from the long axis A, the medium axis B and the short axis C:
- ^ Mass derived from density ρ and the volume V:
- ^ Surface gravity derived from the mass m, the gravitational constant G and the radius r:
- ^ Escape velocity derived from the mass m, the gravitational constant G and the radius r:
References
- ^ Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/
- ^ Jacobson, R. A.; Owen, W. M. Jr. (2004). "The orbits of the inner Neptunian satellites from Voyager, Earthbased, and Hubble Space Telescope observations". Astronomical Journal. 128 (3): 1412–1417. Bibcode:2004AJ....128.1412J. doi:10.1086/423037.
- ^ Showalter, M. R.; de Pater, I.; Lissauer, J. J.; French, R. S. (2019). "The seventh inner moon of Neptune" (PDF). Nature. 566 (7744): 350–353. Bibcode:2019Natur.566..350S. doi:10.1038/s41586-019-0909-9. PMC 6424524. PMID 30787452.
- ^ a b c d Karkoschka, Erich (2003). "Sizes, shapes, and albedos of the inner satellites of Neptune". Icarus. 162 (2): 400–407. Bibcode:2003Icar..162..400K. doi:10.1016/S0019-1035(03)00002-2.
- ^ Zhang, Ke; Hamilton, Douglas P. (2008-01-01). "Orbital resonances in the inner neptunian system: II. Resonant history of Proteus, Larissa, Galatea, and Despina". Icarus. 193 (1): 267–282. Bibcode:2008Icar..193..267Z. doi:10.1016/j.icarus.2007.08.024. ISSN 0019-1035.
- ^ a b "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. Retrieved 2008-12-13.
- ^ Marsden, Brian G. (August 2, 1989). "Satellites of Neptune". IAU Circular. 4824. Retrieved 2011-10-26.
- ^ Marsden, Brian G. (September 16, 1991). "Satellites of Saturn and Neptune". IAU Circular. 5347. Retrieved 2011-10-26.
- ^ Banfield, Don; Murray, Norm (October 1992). "A dynamical history of the inner Neptunian satellites". Icarus. 99 (2): 390–401. Bibcode:1992Icar...99..390B. doi:10.1016/0019-1035(92)90155-Z.
- ^ "Despina | astronomy". Encyclopedia Britannica. Retrieved 2020-11-08.
External links
- Despina Profile by NASA's Solar System Exploration
- Neptune's Known Satellites (by Scott S. Sheppard)
- NASA Astronomy Picture of the Day: Despina and its shadow transiting Neptune (3 September 2009)
- v
- t
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- Naiad
- Thalassa
- Despina
- Galatea
- Larissa
- Hippocamp
- Proteus
Triton |
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Prograde |
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Retrograde |
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