Despina (moon)

Voyager 2 Stephen Synnott

Despina ( Neptune V ) is the third innermost moon of the planet Neptune.

Discovery and designation

Despina was discovered around 28 July 1989 by Stephen P. Synnott on photographic images of the Voyager 2 spacecraft. The discovery was announced on 2 August 1989 by the International Astronomical Union ( IAU); the moon got the provisional designation S/1989 N 3

On September 16, the moon of the IAU was named after the nymph Despina, a daughter of the goddess Demeter and her brother Poseidon in Greek mythology. " Despina " is based on the Greek word for " lady, mistress " and is an epithet, whose real name was known only to the initiated.

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Despina orbiting Neptune on a prograde, nearly perfectly circular orbit at an average distance of 52,526 kilometers (about 2,121 Neptune radii ) from its center, ie 27,762 km above the cloud tops. The orbital eccentricity is 0.0002, the orbit is inclined 0.216 degrees from the equator of Neptune.

The orbit of the next inner moon Thalassa is only 2450 km of Despina's orbit, the moon Galatea of the next outermost 9430 km. Despina ( and Naiad and Thalassa ) is in the midst of the two innermost Neptune Rings, bile - ring (1989 N3R ), which is 10.6 thousand kilometers from Despina orbit removed and the narrow LeVerrier - ring (1989 N2R ) in only 670 km away, where there is already the inner edge of the wide dusty Lassell ring (1989 N4R ).

Despina orbits Neptune in about 8 hours, 1 minute and 54.2 seconds. Since this is faster than the rotation of Neptune, as seen from Neptune Despina goes from the west, and set in the east. Because the rotational period of Neptune with 0.6713 days little more than twice as long, it follows that required at Neptune Despina sky for a full apparent orbit as seen from Neptune Neptune from 0.994 days, so almost as long as the sun. As a result, they are almost in the same place is the end of a day on Neptune Neptune sky as at the beginning of the day, namely a bit more than two degrees to the east.

The moon moves within a critical distance, near the Roche limit, in a descending orbit around the planet and is strong tidal forces exposed. The moon will be at some point torn and train as a ring or crash or burn up in the gas layers of Neptune.


It is believed that Despina synchronously rotates and its axis having an inclination of 0 °.

Physical Properties

Despina is a dark, irregular body with dimensions of 180 × 148 × 128 km and thus the sixth largest of the known moons of Neptune. The average surface temperature is set at -222 ° C ( ~ 51 K ) is estimated. Apparently, the moon was formed by no geological processes after its creation. It is likely that Despina is one of the Rubble Piles that have loosely assembled from fragments of the original moons that are broken apart after Neptune 's largest moon Triton was forced by Neptune on an initially very eccentric orbit.


Despina was discovered as five other inner moons during the Voyager 2 flyby. This low-resolution images could be made that were not smeared in contrast to those of Naiad, Thalassa and Galatea. Since the flyby of Neptune, the system has been extensively studied by ground-based observations as well as with the Hubble Space Telescope. 2002 - 2003 the Keck Observatory observed the system by means of adaptive optics, in which Despina could be located and observed in image processes again. In September 2009, NASA released images from 1989 which showed Despina and caused by it cast shadows on Neptune's clouds.


  • Commons: Despina - album with pictures, videos and audio files
  • Despina, Neptune Moon - Astronomy Picture of the Day on 3 September 2009.