Neptune
What is Neptune?
Planets· Diameter 49,244 km. The windiest world, and the first planet found by mathematics rather than by chance. Its moon Triton orbits backwards — a captured Kuiper belt object.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Neptune is in your sky right now: https://nowsky.org/solar/sky?sel=neptune — location and time set automatically, no login.
Orbit and size
| Diameter | 49,244 km |
|---|---|
| Distance | 30.1 AU |
| Year | 165 yr |
| Winds | up to 2,100 km/h |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Moons of Neptune
Related events
Frequently asked
- How big is Neptune?
- 49,244 km.
- How far is Neptune from Earth?
- 30.1 AU.
- What are the main moons of Neptune?
- Triton.
- Where is Neptune in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Its first birthday since discovery, in 2011
Neptune was discovered on 23 September 1846, and with an orbital period of 164.8 years it returned to the place of its discovery for the first time on 12 July 2011. Humanity has known the planet for less than one of its years. In that single orbit we went from telescopes to spacecraft.
It appears in records before its discovery too. In December 1612 Galileo, observing Jupiter's moons, sketched Neptune right beside them twice and even noted that it had shifted position overnight, but took it for a star. Had he watched a little longer, the history of planet discovery would have moved forward by 234 years. Move the sky view to 28 December 1612 and Neptune reappears next to Jupiter.
The planet in depth
Neptune was the first planet found by calculation rather than search. Le Verrier computed where an unseen body must be to explain Uranus's orbital wobbles; the Berlin Observatory found it that very night in 1846 — Newtonian mechanics' most theatrical triumph.
At 30 AU it receives 1/900th of Earth's sunlight yet hosts the fastest winds known — 2,100 km/h — apparently stirred by heat leaking from its interior. Its big moon Triton orbits backwards, a captured Kuiper Belt object venting nitrogen geysers.
Voyager 2 in 1989 remains the only visitor. Feel the 30-AU distance at true scale in the orbit view — one lap takes 165 years.
Neptune was discovered with pen and paper: as Uranus kept straying off course, Le Verrier computed where an unseen planet must be, and in 1846 the Berlin Observatory found Neptune within a degree of the prediction — Newtonian mechanics' greatest triumph. Its riddles — an interior radiating 2.6 times the sunlight it receives, the solar system's fastest winds at 2,100 km/h — still await an orbiter.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.