Neptune's satellite 1989N1, obtained by Voyager 2 on August 25, 1989 from a range of 146,000 kilometers (NASA)

Proteus (proh'-tee-us, Greek Πρωτέας) is one of Neptune's moons. It is named after Proteus, the shape-changing sea god in Greek mythology.

Proteus was discovered in July, 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 1. It is also designated Neptune VIII.

Physical characteristics

Proteus is more than 400 kilometers in diameter, larger than Neptune's moon Nereid. However, it was not discovered by Earth-based telescopes because it is so close to the planet that it is lost in the glare of reflected sunlight. Proteus is one of the darkest objects in the solar system, as dark as soot; like Saturn's moon Phoebe, it reflects only 6 percent of the sunlight that strikes it. Proteus is very cratered showing no sign of any geological modification. It is also irregularly shaped; scientists believe Proteus is about as large as a body of its density can be without being pulled into a spherical shape by its own gravity.

Data

• Orbital radius: 117,647 km
• Mean diameter: 420 km (440 × 416 × 404)
• Mass: 5.0×10¹⁹ kg
• Estimated density: 1.3 g/cm³
• Orbital period: 1.122 days
• Orbital inclination: 0.026°

See also

• List of craters on Proteus
• Asteroid 9313 Protea

External links

• Animation of Proteus