Proteus is a moon of Neptune, part of the Solar System in the universe. Neptune is a planet associated with the Sun, our star, and this space encyclopedia describes the moon’s identity and place in its planetary system.

Proteus — A natural satellite of Neptune. Its physical properties and orbital motion are shown from the available catalogue and ephemeris data.

No object-specific chemical/elemental dataset has been verified and imported for this record. This does not mean none is publicly available. Appearance may be imagined; chemistry is not.

Discovery and designation
Proteus was discovered in 1989. JPL credits Voyager Science Team. Its provisional designation is S/1989 N1. The name and discovery entry identify this particular satellite of Neptune; similarly named asteroids are separate objects.

Proteus was discovered in 1989 by the Voyager 2 spacecraft. This is unusual since a smaller moon, Nereid, was discovered 33 years earlier using an Earth-based telescope. Proteus was most likely overlooked because it is so dark and the distance between Earth and Neptune is so great.

Proteus is one of the largest of Neptune's known moons, although it is not as big as Triton. The moon has an odd box-like shape and if it had just a little more mass it would be able to transform into a sphere. Proteus orbits Neptune about every 27 hours.

Proteus is irregularly shaped and heavily cratered, but it shows no sign of geological modification. Circling the planet in the same direction as Neptune rotates, Proteus remains close to Neptune's equatorial plane. Proteus is one of the darkest objects in our solar system. Like Saturn's moon Phoebe, Proteus reflects only six percent of the sunlight that hits it.

Proteus is named after the shape-changing sea god of Greek mythology. Proteus was originally designated S/1989 N 1.