Triton
2,707 kmacross
Triton is 2,707 km across and orbits Neptune at 354,800 km, once every 5.9 days (backwards). A captured Kuiper Belt object — it orbits Neptune backwards, and erupts geysers of nitrogen at −235 °C.
▶ Visit Triton in 3D
Why this moon matters
Triton is a stolen world: it orbits Neptune backwards, the signature of a Kuiper Belt object captured whole rather than formed in place — a sibling of Pluto that took a different exit. Voyager 2 photographed geysers of nitrogen erupting through its −235 °C surface, among the coldest measured anywhere. Neptune’s tides are slowly reeling it in; in a few billion years it will tear apart into a spectacular ring.
Triton orbits against Neptune’s spin — the only large moon that does — a giveaway that it didn’t form there but was captured whole.
Triton by the numbers
Diameter
2,707 km
Distance from Neptune
354,800 km
Orbit period
5.9 days (backwards)
Rotation
tidally locked
Surface gravity
0.78 m/s²
Temperature
−235 °C
Orbital speed
4.4 km/s
Sunlight travel time
4.2 hours
In the interactive view you can fly to Triton directly and ride along as it circles Neptune.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.