In Depth | Triton – NASA Solar System Exploration Triton is the largest of Neptune's 13 moons It is unusual because it is the only large moon in our solar system that orbits in the opposite direction of its planet's rotation―a retrograde orbit Scientists think Triton is a Kuiper Belt Object captured by Neptune's gravity millions of years ago
In Depth | Proteus – NASA Solar System Exploration Proteus is one of the largest of Neptune's known moons, although it is not as big as Triton The moon has an odd box-like shape and if it had just a little more mass it would be able to transform into a sphere Proteus orbits Neptune about every 27 hours
In Depth | Moons – NASA Solar System Exploration Of the terrestrial (rocky) planets of the inner solar system, neither Mercury nor Venus have any moons at all, Earth has one and Mars has its two small moons In the outer solar system, the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune have dozens of moons
Solar System Exploration Our solar system includes the Sun, eight planets, five officially named dwarf planets, hundreds of moons, and thousands of asteroids and comets Our solar system is located in the Milky Way, a barred spiral galaxy with two major arms, and two minor arms
Planet Compare - NASA Solar System Exploration NASA’s real-time science encyclopedia of deep space exploration Our scientists and far-ranging robots explore the wild frontiers of our solar system
In Depth | Uranus Moons – NASA Solar System Exploration Cordelia and Ophelia are shepherd moons that keep Uranus' thin, outermost "epsilon" ring well defined Between them and Miranda is a swarm of eight small satellites unlike any other system of planetary moons
In Depth | Kuiper Belt – NASA Solar System Exploration Pieces produced by colliding KBOs can be pushed by Neptune's gravity into orbits that send them sunward, where Jupiter further corrals them into short loops lasting 20 years or less These are called short-period Jupiter-family comets
In Depth | Our Solar System - NASA Solar System Exploration Our solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids