Neptune

Eighth planet from the Sun; is invisible to the naked eye from Earth and appears as an almost featureless, greenish-blue, small disk through a standard telescope.

DATA

Diameter: 49,528km (30,707miles)
Mass: (Earth=1) 17.2
Volume: (Earth=1) 57
Density: (water=1) 2.06
Orbital Period: 164.8 Earth years
Rotation Period: 16 Earth hours, 7 mins, 0 seconds
Av. Surface Temp: -220°C (-364°F)

The Planet Neptune

The upper atmosphere of Neptune is about 85% molecular hydrogen and 15% helium; its mainly blue colour is caused by a trace of methane, which absorbs a lot of light on the red end of the spectrum. Earth’s Voyager 2 probe flew by in 1989 and made several observations of different atmospheric features; faint bands were seen parallel to the equator, there were also spots, the largest an oval spot known as the Great Dark Spot (GDS), about 12,500km (8000 miles) long and 7500km (4500 miles) wide, which is a giant anti-cyclone. Shadows are cast onto a lower cloud deck by white cirrus-type clouds of methane crystals 50km (20 miles) above. Uranus has the highest wind speeds ever recorded by humans, over 2000kph (1250mph) in places.