Proteus (moon) - Definition and Overview

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

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

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 about 400 kilometers in diameter, larger than Neptune's moon Nereid, but it wasn't discovered from Earth-based telescopes because it is so close to Neptune that it is lost in the glare of reflected sunlight. Proteus is irregularly shaped and shows no sign of any geological modification; scientists believe Proteus is about as large as a moon can be without being pulled into a spherical shape by its own gravity. It is heavily cratered.

• 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°

There is also an asteroid named 9313 Protea.

External links

• Animation of Proteus (http://www.star.ucl.ac.uk/~idh/solar/cap/nep/vproteus.htm)