Rotation period (days.hours.min.secs)          16h.7m

Orbital period (days/years)                           164.79y

Orbital speed (miles/km per sec.)                  3.4/5.4

Inclination                                                    1.77 degree

Temperature (F degree/C degree)                 -357/-216

Gravity force (% or X Earth)                         1.2x

Escape velocity (miles/km per second)         14.9/24.0 

Satellites                  At least 8

Special Features    Equatorial winds blow retrograde to rotation; ring wind

Neptune is at this writing the most distant known planet from the Sun. Neptune therefore has been challenging to study from Earth. In spite of this, ground-based astronomers have learned a great deal about this planet, since its position was predicted by John C. Adams in 1845. For example, they have learned that Neptune is composed primarily of Hydrogen and Helium gas, and that its blue color is caused by trace amounts of methane, which absorbs red light. They also detected bright cloud features whose brightness changed with time. They tracked these clouds and were able to infer a rotation period of between 17 and 22 hours.