Proteus, also known as Neptune VIII, is the second-largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology. Proteus orbits Neptune in a nearly equatorial orbit at a distance of about 4.75 times the radius of Neptune's equator.
Processed grayscale image of Proteus from Voyager 2, August 1989 (image processing date)
Voyager 2, the space probe that discovered Proteus
Voyager 2 image of Proteus, digitally processed showing surface features
Image: Neptune visible
Neptune is the eighth and farthest known planet from the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, and slightly more massive than fellow ice giant Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. Being composed primarily of gases and liquids, it has no well-defined solid surface. The planet orbits the Sun once every 164.8 years at an orbital distance of 30.1 astronomical units. It is named after the Roman god of the sea and has the astronomical symbol , representing Neptune's trident.
Galileo Galilei
Urbain Le Verrier, the French astronomer who mostly successfully predicted Neptune's position in the sky using pure mathematics
Johann Gottfried Galle, the German astronomer who was requested by Le Verrier to look for Neptune using the Berlin Observatory's telescope
John Couch Adams, the British astronomer who independently calculated Neptune's position