Neptune
Neptune is the eighth and most distant planet from the Sun. This dark, cold ice giant is whipped by the fastest winds in the solar system, and it holds a unique distinction: it’s the only planet discovered through mathematical prediction rather than direct observation.
| Distance from Sun | 2.8 billion miles (4.5 billion km) — 30 AU |
| Diameter | 30,775 miles (49,528 km) |
| Length of day | about 16 hours |
| Length of year | about 165 Earth years (60,190 Earth days) |
| Moons | 16 known moons |
| Atmosphere | Hydrogen and helium with a small amount of methane |
Interesting facts
- Neptune was the first planet found using mathematical predictions, after astronomers noticed irregularities in Uranus’s orbit — it was spotted almost exactly where the math said it would be, in 1846.
- Neptune has the fastest winds in the solar system, with gusts exceeding 1,200 miles per hour (2,000 km/h).
- Only one spacecraft has ever visited Neptune: Voyager 2, which flew past in 1989.
- Neptune’s largest moon, Triton, orbits backwards compared to the planet’s rotation and is one of the coldest objects in the solar system.
- Galileo may have spotted Neptune in 1612 through his telescope, centuries before its official discovery, but mistook it for a fixed star.
- Neptune’s magnetic field is about 27 times more powerful than Earth’s.