Sun & planets · Space Codex
Neptune
The outermost planet, predicted from Uranus's wobbles before anyone saw it.
Windiest world · found by mathematics
At a glance
Key points
Its winds, up to 580 m/s, are the fastest in the Solar System.
- First planet found by mathematical prediction (1846)
- Completed its first orbit since discovery only in 2011
- Fastest winds in the Solar System
Interior
Like Uranus, Neptune is mostly a hot, dense fluid of water, methane and ammonia over a rocky core of roughly an Earth mass. Unlike Uranus, it radiates more than twice the energy it gets from the distant Sun, and that internal heat drives its violent weather.
Atmosphere and weather
Methane gives a blue tint. Voyager 2 photographed the Great Dark Spot in 1989, a storm about as wide as Earth, which later vanished. In 2025 JWST detected Neptune's auroras for the first time and found its upper atmosphere is now about half as hot as in 1989.
Rings and moons
Five dark rings carry the names of the astronomers linked to Neptune's discovery; the outermost, Adams, holds four bright clumps called arcs. Triton, the largest moon, orbits backward.
Exploration
Urbain Le Verrier predicted Neptune's position from Uranus's orbit, and Johann Galle found it in 1846. Voyager 2's flyby in August 1989 remains the only visit.
What we still don't know
Why Neptune's internal heat is so much stronger than Uranus's, and how its winds reach such speeds on so little sunlight.
Moons
Neptune's moon has its own sourced entry.
- TritonA captured world orbiting backwards
Missions
- 1977–
The only spacecraft to visit Uranus (1986) and Neptune (1989); interstellar since 5 Nov 2018.
- 2021–
Infrared observatory at Sun–Earth L2, about 1.5 million km from Earth.
First-hand · our 3D model
How we render it
Neptune gets the same kind of deep-blue Rayleigh haze shell as Uranus, tuned a little bluer, and three faint ring bands. Its largest moon, Triton, is the one moon in the model that orbits backwards: its 157.3° inclination makes it travel against Neptune's spin, as the real captured moon does.
Sizes and distances in the model are not to scale, so every world can be seen up close. Colour maps are derived from NASA mission imagery via Solar System Scope (CC BY 4.0). The first frame uses light startup maps; higher-resolution maps stream in after the scene is on screen, decoded off the main thread so the page stays responsive.
Related entries
Sources
- JPL Solar System Dynamics: planetary physical parameters (opens in a new tab)
- NASA NSSDC Planetary Fact Sheet (opens in a new tab)
- NASA NSSDC Neptune Fact Sheet (opens in a new tab)
- NASA Science: Neptune moons (opens in a new tab)
- NASA Science: Neptune facts (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.