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Published on June 2nd, 2012 | by Yellow Magpie


Neptune’s Moon Proteus: A Large Irregular World

Neptune’s Moon Proteus

Neptune’s moon Proteus is often overshadowed by its much larger fellow satellite, Triton. It was only recently that this irregular world was discovered offering some very interesting insights in the process.

Physical Characteristics

Neptune’s moon Proteus is roughly 400 kilometres in width (250 miles) orbiting Neptune at a distance of 117,000 km (72,000 miles). It takes the satellite just over one day to complete one rotation of Neptune.

Proteus is an extremely cold world with an average temperature of minus 220 degrees Celsius (minus 360 degrees Fahrenheit).

Second in terms of size to Triton, Proteus is an irregular-shaped Neptunian satellite. Like Triton, Proteus is thought to have not been present during Neptune’s formation.

Neptune's Moon Proteus A Close Up

Neptune’s Moon Proteus Close Proximity

It was only in 1989, when Voyager 2 photographed it, that Proteus was discovered. Like nearly all the moons in the Solar System Proteus has a synchronous orbit. One side always faces Neptune.

The reasons why it took so long for Proteus to be discovered is due to its close proximity to Neptune which obscured it from observation on Earth.

The prevailing thought surrounding Proteus’s orgin is that the satellite was created from the debris surrounding the capture of Triton. When Triton’s orbit became circular the debris would have coalesced to form Proteus.

A Cratered World

Neptune’s moon Proteus is heavily pock-marked. The dark Proteus surface is dominated by craters. The largest crater is Pharos which is 260 kilometres (160 miles) in width.

The Largest Irregular

Interestingly, Proteus is thought to be as large an irregular shape as possible. If Proteus was much larger its own gravity would have caused it to form a sphere.

Highly Recommended Reading

Check out Yellow Magpie’s Planet Neptune: The Mysterious Azure-Blue for more insight into the largest planet in the Solar System.

You may also wish to take a gander at The Solar System And Beyond: A Guide To The Cosmos.

Cosmos is a highly recommended book. It contains large, full-page pictures of the asteroids and writing on the subject by the highly competent author, Giles Sparrow.

For people living in Ireland or the United Kingdom, you can access: Cosmos from here.

For those who live in Canada, you can obtain: Cosmos here.

For Germany: Cosmos.

For France: Cosmos.

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