Astronomy:Despina (moon)
![]() Despina as seen by Voyager 2 (smeared horizontally) | |
Discovery | |
---|---|
Discovered by | Stephen P. Synnott[1] and Voyager Imaging Team |
Discovery date | July 1989 |
Designations | |
Designation | Neptune V |
Pronunciation | /dəˈspaɪnə, dəˈspiːnə, dɛ-/ |
Named after | Δέσποινα Despœna |
Adjectives | Despinian |
Orbital characteristics[2][3] | |
Epoch 18 August 1989 | |
52 525.95 km | |
Eccentricity | 0.00038 ± 0.00016 |
Orbital period | 0.33465551 ± 0.00000001 d |
Inclination |
|
Satellite of | Neptune |
Physical characteristics | |
Dimensions | 180×148×128 km[4][5] |
Mean radius | 78.0 ± 4.7 km[3] |
Volume | ~1.8×106 km3 |
Mass | ~2.2×1018 kg (based on assumed density) |
Mean density | ~1.2 g/cm3 (estimate)[6] |
~0.026 m/s2[lower-alpha 1] | |
~0.063 km/s[lower-alpha 2] | |
Rotation period | synchronous |
Axial tilt | zero |
Albedo | 0.09[4][6] |
Physics | ~51 K mean (estimate) |
Apparent magnitude | 22.0[6] |
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 152 kilometres (94 mi).[9] 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.[10]
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.[11] 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.
![](/wiki/images/thumb/9/9b/Simulated_view_of_Despina.jpg/250px-Simulated_view_of_Despina.jpg)
Notes
- ↑ Surface gravity derived from the mass m, the gravitational constant G and the radius r: Gm/r2.
- ↑ Escape velocity derived from the mass m, the gravitational constant G and the radius r: √2Gm/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. doi:10.1086/423037. Bibcode: 2004AJ....128.1412J.
- ↑ 3.0 3.1 Showalter, M. R.; de Pater, I.; Lissauer, J. J.; French, R. S. (2019). "The seventh inner moon of Neptune". Nature 566 (7744): 350–353. doi:10.1038/s41586-019-0909-9. PMID 30787452. PMC 6424524. Bibcode: 2019Natur.566..350S. https://www.spacetelescope.org/static/archives/releases/science_papers/heic1904/heic1904a.pdf.
- ↑ 4.0 4.1 Karkoschka, Erich (2003). "Sizes, shapes, and albedos of the inner satellites of Neptune". Icarus 162 (2): 400–407. doi:10.1016/S0019-1035(03)00002-2. Bibcode: 2003Icar..162..400K.
- ↑ Williams, Dr. David R. (2008-01-22). "Neptunian Satellite Fact Sheet". NASA (National Space Science Data Center). http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html.
- ↑ 6.0 6.1 6.2 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. http://ssd.jpl.nasa.gov/?sat_phys_par.
- ↑ Marsden, Brian G. (August 2, 1989). "Satellites of Neptune". IAU Circular 4824. http://www.cbat.eps.harvard.edu/iauc/04800/04824.html. Retrieved 2011-10-26.
- ↑ Marsden, Brian G. (September 16, 1991). "Satellites of Saturn and Neptune". IAU Circular 5347. http://www.cbat.eps.harvard.edu/iauc/05300/05347.html. Retrieved 2011-10-26.
- ↑ "Where Are You From? - Credo Reference" (in en). http://search.credoreference.com/content/entry/philipsastronomy/despina/0.
- ↑ Banfield, Don; Murray, Norm (October 1992). "A dynamical history of the inner Neptunian satellites". Icarus 99 (2): 390–401. doi:10.1016/0019-1035(92)90155-Z. Bibcode: 1992Icar...99..390B.
- ↑ "Despina | astronomy" (in en). https://www.britannica.com/topic/Despina.
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)
![]() | Original source: https://en.wikipedia.org/wiki/Despina (moon).
Read more |