Despina (moon)

Moon of Neptune

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.

Notes

^ Volume derived from the long axis A, the medium axis B and the short axis C: ${\frac {\pi }{6}}ABC$
^ Mass derived from density ρ and the volume V: $V\rho$
^ Surface gravity derived from the mass m, the gravitational constant G and the radius r: ${\frac {Gm}{r^{2}}}$
^ Escape velocity derived from the mass m, the gravitational constant G and the radius r: ${\sqrt {\frac {2Gm}{r}}}$

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. 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)

Moons of Neptune

Listed in approximately increasing distance from Neptune

Regular (inner)

Naiad
Thalassa
Despina
Galatea
Larissa
Hippocamp
Proteus

Irregular

Triton	Triton atmosphere climate geology
Prograde	Nereid Sao S/2002 N 5 Laomedeia
Retrograde	Halimede Psamathe Neso S/2021 N 1

See also

Category
Portal

v t e Natural satellites of the Solar System
Planetary satellites of	Earth Mars Jupiter Saturn Uranus Neptune
Dwarf planet satellites of	Orcus Pluto Haumea Quaoar Makemake Gonggong Eris
Minor-planet moons	Near-Earth Florence Didymos Dimorphos Moshup Squannit 1994 CC 2001 SN₂₆₃ Main belt Kalliope Linus Euphrosyne Daphne Peneius Eugenia Petit-Prince Sylvia Romulus Remus Minerva Aegis Gorgoneion Camilla Elektra Kleopatra Alexhelios Cleoselene Ida Dactyl Roxane Olympias Pulcova Balam Dinkinesh (Selam) Jupiter trojans Patroclus Menoetius Hektor Skamandrios Eurybates Queta TNOs Lempo Hiisi Paha 2002 UX₂₅ Sila–Nunam Salacia Actaea Varda Ilmarë Gǃkúnǁʼhòmdímà Gǃòʼé ǃHú 2013 FY₂₇
Ranked by size	Ganymede largest: 5268 km / 0.413 Earths Titan Callisto Io Moon Europa Triton Titania Rhea Oberon Iapetus Charon Umbriel Ariel Dione Tethys Dysnomia Enceladus Miranda Vanth Proteus Mimas Ilmarë Nereid Hiʻiaka Actaea Hyperion Phoebe ...
Discovery timeline Inner moons Irregular moons List Planetary-mass moons Naming Subsatellite Regular moons Trojan moons

Neptune

Outline of Neptune

Geography

Moons

Naiad
Thalassa
Despina
Galatea
Larissa
Hippocamp
Proteus
Triton
Nereid
Halimede
Sao
S/2002 N 5
Laomedeia
Psamathe
Neso
S/2021 N 1

Astronomy

Discovery	Urbain Le Verrier Johann Gottfried Galle John Couch Adams Heinrich Louis d'Arrest William Lassell
General	Kuiper belt Neptune-crossing minor planets
Trojans	385571 Otrera 385695 Clete 2001 QR322 2004 KV18 2005 TN53 2006 RJ103 2007 VL305 2008 LC18 2011 HM102

Exploration

Past	Voyager 2 (1989 flyby)
Proposals	Shensuo Neptune Odyssey ODINUS Triton Hopper Trident
Not selected	Argo Mariner Mark II New Horizons 2