Neptune completes one rotation every 16 hours and 7 minutes. Despite being the slowest-orbiting planet (165 Earth years per orbit), its rotation is faster than Earth's. Neptune generates internal heat equal to 2.6 times what it receives from the Sun, driving supersonic wind speeds up to 2,100 km/h — the fastest sustained winds in the Solar System.
Neptune was discovered in 1846 through mathematical prediction before observation. It has completed just one full orbit since its discovery. Its largest moon, Triton, orbits in the opposite direction to Neptune's rotation and is gradually spiraling inward.
Frequently Asked Questions
How long is a day on Neptune?
Neptune rotates once every 16 hours 7 minutes — about one-third shorter than an Earth day.
How long is a Neptune year?
Neptune takes 165 Earth years to complete one orbit of the Sun.
Why are Neptune's winds so fast?
Neptune generates significant internal heat that drives massive convection currents in its atmosphere, creating wind speeds up to 2,100 km/h.