Between Mars and Jupiter, millions of rocks circle the Sun. They are leftovers from the time the planets were made.
Jupiter's huge gravity kept stirring them up, so they never came together into a planet.
In the movies, spaceships dodge through crowded rocks. The real belt is mostly empty: asteroids are typically a million kilometres apart. Every spacecraft that's crossed it has done so without a scratch.
Put all of it together and you'd have only about 3% of our Moon. More than half of that is in the four biggest: Ceres, Vesta, Pallas and Hygiea.
Look closely at the dots here and you'll see gaps, where Jupiter's pull has cleared certain orbits out. Two swarms of Trojan asteroids share Jupiter's own orbit, one ahead of it and one behind.
- Where
- About 310 to 490 million km from the Sun
- Known asteroids
- Over 1.4 million
- All of it together
- About 3% of the Moon's mass
- Biggest
- Ceres, 940 km wide
