Naiad (moon)
Voyager 2 Richard John Terrile
Naiad Naiad or ( Neptune III) is the innermost and one of the smaller moons of the planet Neptune. He has the shortest orbital period of a planet moon in the solar system.
Discovery and designation
Naiad was the last moon of Neptune, which was discovered during the flyby of the Voyager 2 spacecraft in 1989 by Richard John Terrile probably on or shortly before 18 September. The discovery was announced on 29 September 1989; the moon got the provisional designation S/1989 N 6
On September 16, 1991, the moon of the International Astronomical Union ( IAU ) to the Naiads ( from ancient Greek " flowing water" for "flow" and ) was named, swelling and water nymphs from Greek mythology who, on springs, streams, rivers swamps, ponds, fountains and lakes monitored. They were either daughters of Zeus or of Oceanus. Dried the waters of a naiad, so they had to die.
The name " Naiad " is the English form of the name.
Web properties
Orbit
Naiad orbits Neptune on a prograde, nearly perfectly circular orbit at an average distance of 48,227 kilometers (about 1,947 Neptune radii ) from its center, ie 23,463 km above the cloud tops. This means that it is the Neptune surface closer than Neptune midpoint itself The orbital eccentricity is 0.0004, the web is 4.775 ° relative to the equator of Neptune is inclined, which is compared with the other five prograde regular moons within the Triton track relatively high.
The orbit of the next outer moon Thalassa is only 1840 km of Naiads orbit. Naiad ( and Thalassa and Despina ) are in the middle of the two innermost Neptune Rings, bile - ring (1989 N3R ), which is 6300 km away from the Naiad orbit and the LeVerrier - ring (1989 N2R ) in 4970 km away, where already be the inner edge of the wide dusty Lassell ring (1989 N4R ) is located.
Naiad orbits Neptune in 7 hours, 3 minutes and 55.8 seconds. This is the shortest orbital period of all known planetary moons, even exceeds that of Jupiter's moon Metis by 33 seconds ( Metis exceeds Naiad, however, by its proximity to Jupiter, which is 1.792 Jupiter radii ). Since this is faster than the rotation of Neptune, as seen from Neptune Naiad goes from the west, and set in the east.
Naiad moves within a critical distance, near the Roche limit, in a descending orbit around the planet and will eventually be torn apart as a result of tidal forces into a ring or crash or burn up in Neptune's atmosphere.
Rotation
It is believed that Naiad synchronously rotates and its axis having an inclination of 0 °. Of all the inner moons in the solar system Naiad should have the shortest rotation period. Even shorter rotations are, however, aware of the irregular moons of Saturn and Hati Mundilfari.
Physical Properties
Naiad is a very dark, irregularly shaped body with 96 × 60 × 52 km across. He is the smallest of the inner regular moons of Neptune and the eighth largest in the Neptune system, but what could possibly be surpassed by the 2002 irregular moons discovered Halimede and Neso, they should be darker than expected. The mean surface temperature of the Naiad is at -222 ° C ( ~ 51 K ) is estimated. Apparently, the moon was formed by no geological processes after its creation. It is likely that Naiad 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.
Research
Since Naiad was only discovered during the Voyager 2 flyby, could - caused by the movement of the probe - only smeared images of Naiad be made. Since the flyby of the Neptune system ground-based observations as well as the Hubble Space Telescope has been studied intensively. 2002 - 2003 the Keck Observatory observed the system by means of adaptive optics, and which, although the four largest inner moons were found, in contrast to the next outer Naiad Thalassa, however, could not be located. Despite the ability of Hubble to find all known moons, and perhaps also to discover new ones that are even fainter than Voyager 2, Naiad was still not found. It is suspected that this is due to errors in Naiads ephemeris.
In October 2013, the SETI Institute announced after 24 years, the rediscovery of the moon. By the scientists placed one above the other archival images from the Hubble telescope in 2004 and so a longer exposure time simulated, they were able to identify Naiad.