Triton
What is Triton?
Moons· Diameter 2,707 km. The only large moon orbiting backwards — likely a captured Kuiper belt object, with nitrogen geysers at −235 °C.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
The orbit of Triton at this moment: https://nowsky.org/solar/orbit?fw=moon:neptune:triton&sp=0.008 — replayed live, no login.
Orbit and size
| Diameter | 2,707 km |
|---|---|
| Parent | Neptune |
| Note | retrograde — a captured body |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Parent planet and sibling moons
Frequently asked
- How big is Triton?
- 2,707 km.
- What is notable about Triton?
- retrograde — a captured body.
- Which planet does Triton orbit?
- Neptune.
Cantaloupe terrain — ice like a melon rind
The western hemisphere Voyager 2 photographed is covered with dimples about 30 km across, packed so densely that it was compared to the rind of a cantaloupe. They are not impact craters — too uniform in size and never overlapping. They are read instead as the marks of ice slowly overturning, a dense layer beneath the crust trading places with a lighter one and doming the surface. No other body in the solar system shows the pattern.
Triton's surface, at −235 °C, is among the coldest ever measured. Yet when sunlight warms nitrogen ice enough to turn it to gas beneath the surface, it bursts out in dark plumes 8 km high — the ice sits so close to a thermal edge that a rise of a few degrees is explosive. Voyager also caught the soot from those geysers carried downwind into long streaks toward the south-west.
The moon in depth
Triton is the only large moon orbiting backwards — not born of Neptune but captured, most likely a Kuiper Belt object like Pluto. A pristine Kuiper world, held on a leash beside Neptune.
Voyager 2's 1989 flyby revealed a −235 °C surface with nitrogen geysers rising in 8-km black columns — the coldest measured world in the solar system, and still active, its terrain wrinkled like a cantaloupe rind.
Retrograde orbits carry a death sentence: tides are slowly dragging Triton inward, and in a few billion years it will shatter into a great ring around Neptune. Zoom to Neptune in the Orbit view to watch it circle the wrong way.
Triton is almost certainly a captured Kuiper Belt object — the only large moon orbiting backward against its planet's spin, and a near-twin of Pluto in size and makeup. Tidal forces are slowly reeling it in; billions of years from now it will shatter into a ring grander than Saturn's. Voyager 2's shots of its nitrogen geysers remain our only close look.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.