More than 30 times as far from the Sun as Earth, Neptune is the
only planet in our solar system not visible to the naked eye and the
first predicted by mathematics before its discovery. In 2011 Neptune
completed its first 165-year orbit since its discovery in 1846.
Neptune takes about 16 hours to rotate once (a Neptunian day),
and about 165 Earth years to orbit the sun (a Neptunian year).
Neptune has 13 moons (and one more awaiting confirmation of discovery),
which are named after sea gods and nymphs in Greek mythology.
It has six known moons. Because of dwarf planet Pluto’s elliptical orbit,
Pluto is sometimes closer to the Sun (and us) than Neptune is.