Neptune is the outermost of the four gas giants: Jupiter, Saturn, Uranus, Neptune. Because of its distance from the Sun, Neptune's atmosphere is a frigid -225° C (-373° F). The blue-green color of the planet is due to the presence of methane in the atmosphere. The atmosphere consists mostly of hydrogen, helium and methane. Until the Voyager encounter in 1989, the rings surrounding Neptune were thought to be arcs. We now know that the rings completely circle the planet, but the thickness of each ring varies along its length. If you weigh 90 pounds on Earth, you would weigh about 103 pounds on Neptune

Discoverer(s): Galle, Challis, Adams, & Le Verrier (1846)
Spacecraft Encounter(s): Voyager 2
Mean Distance from the Sun: 30.06 AU (4.5 billion km/2.8 billion mi)
Length of year: 165 years
Rotation period: 16.11 hours
Mean orbital velocity: 5.43 km/s (3.3 mi/s)
Diameter: 50,538 km
Inclination of axis: 29.6°
Number of observed satellites: 8