Sunday, September 6, 2009

The Innermost moons of Neptune

The Innermost moons of Neptune

In 1989, Voyager 2 found some small tiny bodies revolving around Neptune closely..They were the 4 innermost moons of Neptunes and Very small in size....

1. Naiad ( "NAY ed" ) is the innermost of Neptune's known satellites:

orbit: 48,200 km from Neptune
diameter: 58 km
mass: ?

The Naiads were the nymphs who lived in and presided over brooks, springs, and fountains.

The last of the satellites discovered in 1989 by Voyager 2.

2. Thalassa ("tuh LASS eh") is the second of Neptune's known satellites:

orbit: 50,000 km from Neptune
diameter: 80 km
mass: ?

Thalassa was a daughter of Aether and Hemera. "Thalassa" is also the Greek word for "sea".

Discovered in 1989 by Voyager 2.

3. Despina is the third of Neptune's known satellites:

orbit: 52,600 km from Neptune
diameter: 148 km
mass: ?

Despina was a nymph, the daughter of Poseidon (Neptune) and Demeter.

Discovered in 1989 by Voyager 2

4. Galatea ("gal eh TEE eh") is the fourth of Neptune's known satellites:

orbit: 62,000 km from Neptune
diameter: 158 km
mass: ?

Galatea was a Sicilian Nereid loved by the Cyclops Polyphemus. (Not related to the maiden who was originally a statue carved by Pygmalion and who was brought to life by Aphrodite.)

Other moons of Neptune

Apart from the above quoted moons of Neptune, the next one out, Larissa, was actually discovered in 1981, when it blocked a star. This was attributed to the ring arcs, but later was found to be the moon, being re-discovered by Voyager 2 in 1989.

Proteus is the second-largest moon in orbit around Neptune. It is so close to the planet that Earth-bound telescopes cannot see it.

Triton is next (right), and is one of the strangest moons in the solar system. First, it is one of only three moons in the solar system that has an atmosphere (Jupiter's Io and Saturn's Titan are the other two). It is thicker than Io's, yet much thinner than Titan's. Its pressure is 1/100,000 of Earth's.


Second, Triton has a retrograde orbit, which means that it orbits the opposite way the planet spins. This is a very strong indication that Triton was captured. This in itself is not strange; both of Mars' moons were captured. What is strange is that Triton is two-thirds the size of our moon. When two bodies have a close encounter, one does not automatically capture the other, especially if it is so big. One theory is that Triton must have actually hit Neptune, bounced off the atmosphere, and gone into orbit because it lost all of its momentum. Another way this could have happened is that Triton collided with one of Neptune's moons, smashed it to bits (possibly creating the rings), and lost so much momentum that it couldn't escape Neptune's gravity.

Third, it is only 38 °C (100 °F) above absolute zero (the temperature at which all matter comes to rest). In such frigid a climate scientists did not expect to find active geysers. But, they did. They spew out a gaseous form of nitrogen, which is what creates its atmosphere.

The eighth moon, Nereid, has a highly elliptical orbit that causes it to swing around Neptune at various distances. When closest, it is 1,342,530 km (834,210 miles) from the planet. At the farthest distance, it is 9,667,120 km (6,006,870 miles) from Neptune.

The last five moons were discovered in the first few weeks of and throughout 2003. They have not yet been given official names by the International Astronomical Union. Very little is yet known about them.

Data for Neptune's Moons

Name Discovery Date Discoverer Distance from Neptune(10^3 km) Mass(10^20 kg) Radius (km) Orbital Period (days)
Naiad (NIII) 1989 Voyager 2 48.227 0.002 29 0.294
Thalassa (NIV) 1989 Voyager 2 50.075 0.0004 40 0.311
Despina (NV) 1989 Voyager 2 52.526 0.02 74 0.335
Galatea (NVI) 1989 Voyager 2 61.953 0.04 79 0.429
Larissa (NVII) 1989 Voyager 2 73.548 0.05 104x89 0.555
Proteus (NVIII) 1989 Voyager 2 117.647 0.5 218x208x201 1.122
Triton (NI) 1846 W. Lassel 354.76 214 1353.4 5.877*
Nereid (NII) 1949 G. Kuiper 5513.4 0.3 170 360.136
S/2002 N1 2002 15,686 0.001 24 1874.8
S/2002 N2 2002 22,452 0.001 24 2918.9
S/2002 N3 2002 22,580 0.001 24 29.82
S/2002 N4 2002 46,570 30 8863.1*
S/2003 N1 2003 46,738 0.0002 14 9136.1*


Titan or Saturn VI is the largest moon of Saturn, the only moon known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.

Titan is the twentieth most distant moon of Saturn and sixth farthest among those large enough to assume a spheroid shape. Frequently described as a satellite with planet-like characteristics, Titan has a diameter roughly 50% larger than Earth's moon and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter's moon Ganymede, and it is larger by volume than the smallest planet, Mercury, although only half as massive. Titan was the first known moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens.

Titan is primarily composed of water ice and rocky material. The dense atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in the satellite's polar regions. These are the only large, stable bodies of surface liquid known to exist anywhere other than Earth. The surface is geologically young; although mountains and several possible cryovolcanoes have been discovered, it is relatively smooth and few impact craters have been discovered.

The atmosphere of Titan is largely composed of nitrogen and its climate includes methane and ethane clouds. The climate—including wind and rain—creates surface features that are similar to those on Earth, such as sand dunes and shorelines, and, like Earth, is dominated by seasonal weather patterns. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan is viewed as analogous to the early Earth, although at a much lower temperature. The satellite has thus been cited as a possible host for microbial extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry. Researchers have suggested a possible underground liquid ocean might serve as a biotic environment.

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