By far the most numerous objects in the solar system are asteroids — chunks of rock, metal, and ice. Scientists have discovered more than 1.3 million of them. They range from a few feet across to a few hundred miles. Most of them reside in the asteroid belt, between the orbits of Mars and Jupiter.

Until a few decades ago, the number of known asteroids was just a few thousand. But some asteroids can come close to Earth, possibly endangering our planet. So scientists launched big searches to find as many as possible. As the searches continue, the known asteroid population goes up by tens of thousands every year. Fortunately, almost all of the asteroids are no danger to Earth.

There are three major classes of asteroids. The most common are class C — they contain a lot of carbon. They account for roughly three-quarters of all asteroids. Next is class S. These objects are rich in silicon, so they’re like a lot of the rocks on Earth. And class M asteroids contain a lot of metal.

The largest object in the asteroid belt is Ceres — about 600 miles in diameter. It was the first asteroid ever discovered. Today, it’s classified as a “dwarf planet.” But when scientists study the overall story of asteroids, they still include Ceres.

Despite their numbers, asteroids don’t add up to much. Their total mass is only three percent of the mass of the Moon. So they’re basically little chips floating through the solar system.

Script by Damond Benningfield