Triton

Triton orbits Neptune backwards and has icy volcanoes that erupt nitrogen!

What it is

Neptune's largest moon, orbits backwards, likely a captured dwarf planet with active nitrogen geysers.

Moon: Orbits a planet rather than the star. Every kind of thing there is →

Its position moves, so there is no fixed place on a map to point at. The Planetarium works out where it is for your own place and date.

A tiny point right beside its bright planet — steady the telescope and wait.

Triton is a bit smaller than our Moon. In weight, about 1/280th of Earth. Its day: tidally locked; same as its orbital period, 5.88 days.

Its surface: Orbits backwards compared to Neptune's spin -- likely a captured dwarf planet; has active nitrogen geysers.
How it moves: Less than a week -- and it goes backwards, opposite to Neptune's spin!
The machines we sent: Voyager 2 (1989) -- the only spacecraft to ever visit.

The numbers

Across	2 707 km
Distance from the planet it orbits	354 759 km
Once round its orbit	-141.0 hours
One spin	5.9 days
Temperature	-235 °C (from -235 to -235)
Made of, among other things	nitrogen, methane, water

Nobody flew a tape measure out there. Every number on this page was worked out from the ground:

Clear tonight? The Planetarium will show you what is worth a look. Then just go out.