Ganymede is the biggest moon of all — even bigger than the planet Mercury!
Largest moon in the solar system, bigger than Mercury, only moon with its own magnetic field.
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.
Honest, not glamorous — why the pictures here are drawn.
Ganymede is bigger than the planet Mercury! The largest moon in the solar system. In weight, about 1/40th of Earth. Its day: tidally locked; same as its orbital period, 7.15 days.
| Across | 5 268 km |
|---|---|
| Distance from the planet it orbits | 1 070 412 km |
| Once round its orbit | 7.2 days |
| One spin | 7.2 days |
| Made of, among other things | water, rock (basalt) |
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.