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Halimede is one of the three tiniest moons of Neptune along with Sao and Laomedeia. It is so small, faint, and distant, that it was missed by the Voyager spacecraft in 1989. However, it was discovered in 2002 by a team of astronomers using sophisticated ground based telescope systems. It cannot be seen by the naked eye as it is 100 million times too distant and dim.

In everyday English, the word ‘eccentric’ means something or someone that is conspicuously or grossly unconventional or unusual. In the world of astronomy, an eccentric orbit is one that is not circular in nature, but more elliptical. Halimede has an orbit that is considered eccentric along with four other moons of Neptune: Laomedeia, Psamathe, Neso, and Neried (the most eccentric of all the moons).

Halimede also has a retrograde orbit, meaning that it orbits in the opposite direction of Neptune’s planetary rotation. It takes a bit over five Earth years to orbit Neptune due to the wide elliptical nature of its orbit. At only 62 kilometers in diameter, it is theorized that it could have once been a part of Neptune’s third largest moon, Neried, due to its remarkably similar physical characteristics to the larger moon. Astronomers theorize that there is a high probability that Halimede was formed by a collision with Neried at some point during the formation of the solar system.

Not much else is known of Halimede and her eccentric sisters, Sao and Laomedeia; however, scientists are eager to learn more about them. Doing so may offer insight into the planetary and cosmic condition of our solar system during its formation billions of years ago. Astronomers from around the world are working in a unified effort to accomplish this important task.

Astronomer, Kuiper, named the third largest moon of Neptune, but the second to be discovered, Nereid. A Nereid is the name used to collectively refer to the fifty daughters of Nereus and Doris of Greek mythology who attended to Poseidon’s, the Greek sea god, every need. Neptune’s other moons are named following this same theme. Other Nereids from mythology are Halimede, Laomedeia, Neso, Galatea, Psamathe, and Sao – other moons of Neptune! Other moons of Neptune include Naiad, a river nymph, Thalassa, Greek for ‘sea’, Larissa, Poseidon’s lover, and Despina, the nymph daughter of Poseidon and Demeter. The two moons named after males are the two largest, Proteus and Triton. Both are sons of Poseidon in mythology.

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