The Thirteen Satellites
Neptune has thirteen known satellites, or moons. They are named for aquatic personages in Greek and Roman mythology. There are five which were recently discovered in these past years. Four were discovered in the year of 2002 and one in 2003, all by astronomers using improved ground-based telescopes. Six of these moons, Despina, Galatea, Larissa, Naiad, Proteus and Thalassa, were found by the Voyager 2 Spacecraft.
Neptune’s largest satellite, Triton, has a diameter of about 2,700 kilometers. The rest of Neptune’s satellites are much smaller than Triton. Proteus is the second largest satellite, and after that is Nereid. The interesting thing about Proteus is that it has an oddly distorted shape. It is non-spherical, but instead, quite irregular. Nereid has an orbit of which is the most highly eccentric of any planet or satellite in the solar system.
Triton: Neptune's Largest Satellite
Triton is by far, Neptune’s largest Satellite. With a whopping diameter of 2,700 kilometers, it stands out from the rest of Neptune’s satellites. It is about 354,760 kilometers away from Neptune and it’s the only major satellite in the solar system that revolves in a direction opposite to that of its planet. Triton travels around Neptune every six days, within a circular orbit. This giant has a surface temperature of a brisk -390 Fahrenheit. Now that’s cold! In fact, it is the coldest known temperature in our Solar System. Although, scientists have discovered evidence that Triton once had volcanoes, which spewed a slushy mixture of ammonia and water.
Neptune's Satellites
| Satellites | Discovery Date | Discovery Location |
| Triton | October 10, 1846 | Liverpool |
| Nereid | May 1, 1949 | Fort Davis |
| Naiad | August 1989 | Voyager 2 |
| Thalassa | August 1989 | Voyager 2 |
| Despina | July 1989 | Voyager 2 |
| Galatea | July 1989 | Voyager 2 |
| Larissa | July 1989 | Voyager 2 |
| Proteus | June 1989 | Voyager 2 |
| Halimede | August 14, 2002 | Cerro Tololo |
| Psamathe | August 29, 2003 | Mauna Kea |
| Sao | August 14, 2002 | Cerro Tololo |
| Laomedeia | August 13, 2002 | Cerro Tololo |
| Neso | August 14, 2002 | Cerro Tololo |