Synnott City
( /ˈprtəs/;[e] Greek: Πρωτεύς), also known as Neptune VIII, 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 circles Neptune in a nearly equatorial orbit at the distance of about 4.75 equatorial radii of the planet.

Despite being more than 400 km in diameter Proteus has a somewhat irregular shape with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color and heavily cratered. The largest crater is more than 200 km in diameter. There are also a number of scarps, grooves and valleys related to large craters.

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.

Commander Tanaka Tsuno was the first human to set foot on Proteus on March 5th 2101 (as part of the the Greater Solar System Survey Project : Pandect II 2100 - 2102)

Synnott City, the first Settlement was established only six month later at the End of September 2101. Proteus became an Industrial Center early on and became famous for the place where the RAID Virus was developed. The Town Nils Place on the Neptune Face Side is one of the most famous micro biology research centers in the Union. (Proteus-Nils Microbiology University)

Voyager City the Capitol of Proteus Moon is also the seat of the National Galactic Society, the National Geographic photographic museum and the Sol System Colonization Museum. The NGS later established a Natural History Museum outside of Voyager City that developed into the largest Natural History Museum in the Union and spawned its own town with 200,000 inhabitants. Museum Town is visited annually by over 5 million visitors and many times that in virtual tour visitors. A very specialized Industry of Museum display manufacturers, Natural History artifact collector speiality shops and Artifact dealers has developed around that Museum. Specimen collector societies, meetings and conferences are held here as well. The trade in such Speciment became the main Import and export Item traded via the Proteus Xchange. The Moon is represented at the Assembly via the Neptune Moon Representative (of All Neptune Moons) Law, Government and Civics are based and managed from Triton Moon.


  • Discovered by Voyager 2
  • Stephen P. Synnott
  • Discovery date June 16, 1989


  • Adjective Protean
  • Orbital characteristics
  • Epoch 18 August 1989
  • Periapsis 117,584 ± 10 km
  • Apoapsis 117,709 ± 10 km
  • Semi-major axis 117,647 ± 1 km (4.75 RN)
  • Eccentricity 0.00053 ± 0.00009
  • Orbital period 1.12231477 ± 0.00000002 d
  • Average orbital speed 7.623 km/s
  • Inclination 0.524° (to Neptune equator)
  • 0.026 ± 0.007° (to local Laplace plane)
  • Satellite of Neptune
  • Proper orbital elements
  • Physical characteristics
  • Dimensions 424×390×396 km
  • Mean radius 210 ± 7 km[5]
  • Volume 3.4 ± 0.4 ×107km³
  • Mass 4.4×1019 kg[b]
  • Mean density ~1.3 g/cm³ (estimate)
  • Equatorial surface gravity 0.07 m/s2
  • Escape velocity 0.17 km/s[d]
  • Rotation period synchronous
  • Axial tilt zero
  • Albedo 0.096
  • Temperature ~51 K mean
  • Apparent magnitude 19.7
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