Neptune’s largest moon. It orbits backwards, is probably a captured dwarf planet, and has active nitrogen geysers.
No small telescope will show you this one; it is here to be understood, not spotted.
Triton is roughly four fifths as wide as the Moon.
Triton sits about nine tenths of the Earth-to-Moon distance from Neptune.
Triton takes about 5.9 Earth days to go once round Neptune.
Triton turns round once in about 5.9 Earth days; Earth takes about 24 hours. Its orbit takes exactly as long, so Triton keeps the same face turned towards Neptune the whole time. And Triton spins backwards.
Triton has roughly one quarter the mass of the Moon.
Triton has roughly half the volume of the Moon.
On Triton you would weigh roughly one thirteenth of what you weigh on Earth.
On Triton it is −235 °C. Earth runs from −89.2 to 56.7 °C.

| Across | 2,705 km |
|---|---|
| Distance from the centre of the planet it orbits | 354,759 km |
| Once round its orbit | 5.877 days |
| One spin | 5.877 days — and it turns the other way, so the Sun there rises in the west |
| Temperature | −235 °C |
| Also found there | nitrogen, methane, water |