Proteus

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Proteus
Proteus is the second largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology. Proteus orbits Neptune in a nearly equatorial orbit at the distance of about 4.75 equatorial radii of the planet. Despite being a predominantly icy body more than 400 km in diameter, Proteus's shape deviates significantly from an ellipsoid. It is shaped more like an irregular polyhedron with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color, and heavily cratered. Proteus is probably not an original body that formed with Neptune; it may have accreted later from the debris created when the largest Neptunian satellite Triton was captured. Proteus (moon) - Wikipedia, the free encyclopedia
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Short Description Proteus is the second largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology. Proteus orbits Neptune in a nearly equatorial orbit at the distance of about 4.75 equatorial radii of the planet. Despite being a predominantly icy body more than 400 km in diameter, Proteus's shape deviates significantly from an ellipsoid. It is shaped more like an irregular polyhedron with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color, and heavily cratered. Proteus is probably not an original body that formed with Neptune; it may have accreted later from the debris created when the largest Neptunian satellite Triton was captured. Proteus (moon) - Wikipedia, the free encyclopedia
Discovered by Voyager 2 Stephen P. Synnott
Discovery date June 16, 1989
Type Moon
AddInfo Neptune VIII
Satellite of Neptune
Orbit Prograde
Rotation Synchronous
Apoapsis 06 117 709 km
Periapsis 06 117 584 km
Semi-major axis 06 117 647 km
Distance from Sun 02 30.110 387 au /06
Eccentricity 0.000 53
Orbital period 1.122 314 77 day
Orbital speed 01 7.623 km/s
Inclination to the ecliptic 028.92°
Inclination to the equator 000.524°
Diameter/Size 03 420 ± 7 km
Dimensions 424 × 390 × 396 km
Mass 1019×4.4 kg
Density 01 1.3 g/cm3
Surface gravity  0.07 m/s2
Escape velocity  170 m/s
Rotation period 1.122 314 77 day
Axial tilt
Albedo geometric 0.096
Temperature mean 02 51 K | -222 °C
Apparent magnitude 19.7
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