Cosmic Scale
Neptune
Ice giant · 4.5 billion km from the Sun
How big is Neptune?
Neptune is about 49,240 km across.
See Neptune in 3D, at true scale
Neptune was found with mathematics before anyone looked: astronomers noticed Uranus was being tugged off course, calculated where the culprit must be, and pointed a telescope there in 1846. It is an ice giant with the fiercest winds in the Solar System.
At a glance
| Diameter | 49,240 km |
|---|---|
| Mass | 1.02 × 10²⁶ kg |
| Diameter compared with Earth | 3.86 × Earth |
| Year | 165 years |
| Day | 16 hours |
| Winds | Up to 2,100 km/h |
| Moons | 16 known |
Good to know
- It has completed only one orbit since its discovery, in 2011.
- Its blue colour comes from methane absorbing red light — though its true shade is paler than the famous Voyager images suggest.
- Voyager 2, in 1989, is the only spacecraft ever to visit.
- Next smaller: 55 Cancri e · 23,950 km
- Next larger: Uranus · 50,720 km