Neptune rotates completely on its axis once every 16 hours and orbits the sun once in 164.79 Earth years. Its albedo, or reflectivity, is high (84 percent of the light falling on it is reflected), but it is so far away from the earth its stellar magnitude (a scale used to describe the brightness of an astronomical object; lower numbers correspond to brighter objects,is only 7.8, which means it is never bright enough to be seen with the naked eye from earth. When observed through a telescope, it appears as a greenish-blue disk without any definite surface markings. However, images from the Voyager 2 probe, which flew past Neptune in 1989, and the Hubble Space Telescope, which observed Neptune in 1994, have revealed dynamic bright and dark spots in Neptune's atmosphere that are thought to be huge storms caused by the difference in temperature between the heat-producing core and the frigid cloud tops. Voyager 2 measured wind speeds of 2400 km/h (1500 mph), the highest on any planet.

Neptune is orbited by five thin rings and eight known satellites, two of which are observable from Earth. The largest and brightest is Triton, discovered in 1846, the same year Neptune was first observed. Triton, with a diameter of 2705 km (1680 mi), is only slightly smaller than Earth's moon. It has a retrograde orbit—that is, opposite the direction of rotation of the body that it orbits. Despite its extreme coldness, Triton has a nitrogen atmosphere with some methane and some form of haze, and it displays an active surface of geysers that spout an unknown subsurface material. Triton is slowly spiraling in toward Neptune; in 10 million to 100 million years it is expected to be so close to Neptune that it will be pulled apart by gravitational forces, its remnants adding to Neptune's five rings. Nereid, the second satellite (discovered in 1949), has a diameter of only about 320 km (about 200 mi). Six more satellites were discovered by the Voyager 2 planetary probe in 1989.