08 · ice giant

Neptune

The last giant. Dark storms, the fastest winds in the system, and a blue that is methane, not water.

Distance from Sol

4.50 bn km

Surface gravity

11.2 m/s²

Day length

16.1 hrs

Mean temperature

−201 °C

Orbital period

165 yrs

Atmosphere

80% hydrogen, 19% helium, 1.5% methane. Winds reach 2,100 km/h. The Great Dark Spot seen by Voyager 2 in 1989 had vanished by Hubble's first look in 1994. New ones form.

Notes

Predicted by mathematics before it was seen. Adams and Le Verrier computed the pull on Uranus; Galle found it in 1846 within a degree of the prediction. It has completed one orbit since discovery in 2011.

Illustrative scale · orbital distances compressed. Not an ephemeris.