How many space rocks are there?
Billions and billions. Astronomers have found more than a million asteroids, and there are countless smaller pieces, down to specks of dust.
Space rocks come in all sizes, from dust grains to objects hundreds of kilometres wide, and there are an astonishing number of them.
Astronomers have discovered more than 1.4 million asteroids so far, and new ones are found every night. Most travel around the Sun in the asteroid belt, between Mars and Jupiter. The largest, Ceres, is about 940 kilometres across, almost as wide as France. But most are much smaller, and the smaller they are, the more of them there are. Scientists estimate there are more than a million asteroids larger than a kilometre in the main belt, and many millions of smaller ones.
Around the Solar System are also trillions of comets, mostly far beyond the planets in a giant cloud called the Oort Cloud. Then there are countless pebbles and dust grains, the bits that make shooting stars. Scientists think thousands of tonnes of space dust fall on Earth every year.
Even though there are so many, space is enormous. The asteroids in the asteroid belt are usually hundreds of thousands of kilometres apart, so spacecraft fly through the belt without danger. If you stood on one asteroid, you would usually not even see the next one.