Moon of Neptune · Updated May 2026
Triton.
Triton is the largest moon of Neptune at 2,707 km diameter — and the only large moon in the solar system with a retrograde orbit (it goes the opposite way to its planet's rotation). That tells us Triton was almost certainly captured from the Kuiper Belt rather than forming alongside Neptune. It also has active geysers of nitrogen gas.
View Neptune system in 3D →Key facts
Voyager 2 saw active nitrogen geysers shooting 8 km up from Triton's surface in 1989 — making it one of only a handful of geologically active worlds known. Triton's surface temperature, around -235 °C, is the coldest measured anywhere in the solar system.
About Triton
Triton's retrograde orbit guarantees it will eventually spiral inward and be torn apart by Neptune's tidal forces — but not for billions of years. Its surface is young, with few impact craters, suggesting ongoing resurfacing. A possible subsurface ocean has been proposed.
How to view Triton in 3D
Triton orbits Neptune in real time inside the interactive viewer. Open the parent body to see the orbital geometry, or use the object browser to fly directly to the moon and observe its rotation, surface, and orbit.
Open the Neptune system →Sources & methodology
Numbers cross-referenced with the sources below; updated May 2026.