Neptune
49,244 kmacross
Neptune is 49,244 km across (3.9× wider than Earth) and orbits the Sun at 30.1 AU — about 4,502,895,887 km. Sunlight takes 4.2 hours to reach it. The outermost planet — a deep blue, storm-wracked ice giant discovered by mathematics before it was ever seen.
▶ Visit Neptune in 3D
What kind of world is it?
Neptune was found in 1846 exactly where mathematicians said an unseen planet must be, from the way it tugged on Uranus — the first world discovered by prediction rather than accident. It has completed just one orbit of the Sun since. How the dimmest, coldest planet powers the fastest winds in the solar system is still not fully understood.
Winds on Neptune top 2,100 km/h — the fastest in the solar system — yet it receives 900× less sunlight than Earth.
Neptune by the numbers
Diameter
49,244 km
Distance from the Sun
30.1 AU
Sunlight travel time
4.2 hours
Surface gravity
11.2 m/s²
Temperature
−200 °C
A day lasts
16 hours
A year lasts
165 Earth years
Known moons
18
Notable moons
Neptune has 18 known moons. The ones worth meeting:
Numbers only get you so far. The distances are the part nobody's brain handles — in the interactive view, switch to 1:1 scale and watch Neptune shrink to an honest speck on an enormous empty orbit.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.