Neptune is the last of the hydrogen and helium gas giants in our solar system.
The planet takes almost 165 Earth years to orbit our sun
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Discovery
Urbain Le Verrier, John Couch Adams, Johann Galle
Since Neptune was named for the Roman god of the sea, its moons were named for various lesser sea gods and nymphs in Greek mythology.
Triton (not to be confused with Saturn's moon, Titan), is far and away the largest of Neptune's satellites. Dutch-American astronomer Gerard Kuiper (for whom the Kuiper Belt was named) found Neptune's third-largest moon, Nereid, in 1949. He missed Proteus, the second-largest, because it's too dark and too close to Neptune for telescopes of that era. Proteus is a slightly non-spherical moon, and it is thought to be right at the limit of how massive an object can be before its gravity pulls it into a sphere.