Proteus is the largest moon that is not fully spherical in shape. It probably an asteroid that was captured from the Oort cloud when it strayed too closely. It is the second largest of the Neptunian moons. The largest is Triton, which accounts for 95% of all objects that are currently in orbit round Neptune. Proteus is a Moon that orbits round Neptune rather than the Sun which our Earth orbits round. Its orbit circumference, the total distance it travels round its planetary parent is 739,191.57 km. The furthest it gets from its orbital parent (apoasis) is 117,705 km. Its mass is estimated/calculated at being 50,355,259,352,065,700,000 kg. Its density has been calculated at being 1.3 g/cm3. Its volume is 1.3 g/cm3. It was discovered in the year 1989 by S. Synnott, Voyager 2.

The Semi-Major Axis of the orbit is 117,646 km, which is the furthest point from the centre to the edge of an elliptical point.

The mass of the object is calculated at being 50,355,259,352,065,700,000 kg. The equatorial circumference of Proteus is 1,319.5 km. The mean radius of Proteus is 210.0 km. The surface area of Proteus is 554,176.94 km2. The surface gravity of the said item is 0.76 m/s2. The average orbit velocity, that is the speed at which it orbits is 27,450.7 km/h.

The orbital inclination, the angle at which Proteus orbits in relation to the orbital plane is 0.075 degrees. The orbital eccentricity is 0.0005, it is the degree at which Proteus orbits close to a circular (0) orbit as opposed to an elliptical (1) orbit.