Voyager 2 discovered six moons orbiting Neptune, but only three were photographed in detail: Proteus, Nereid, and Triton. Proteus turned out to be an ellipsoid, as large as an ellipsoid could become without turning into a sphere. Proteus is very dark in color. Nereid, although discovered in 1949, is still not well known even after Voyager 2 passed by. Triton was flown by at about 25,000 miles (40,000 km) away, and became the last object Voyager 2 would ever explore. Triton was shown to have extraordinary active geysers and polar caps. A very thin atmosphere was found, as well as thin clouds.