Asteroids are small, rocky objects that orbit the Sun. There are millions of asteroids in the solar system, ranging in size from pebbles to mountains. Most asteroids are found in the asteroid belt, a region between the orbits of Mars and Jupiter.
Asteroids are thought to be leftovers from the formation of the solar system. They are made mostly of rock and metal, with a few icy bodies mixed in. Asteroids vary greatly in size and shape, but they all have one thing in common: they’re much smaller than planets.
The largest asteroid is Ceres, which is about 950 kilometers (590 miles) across. It’s also the only asteroid classified as a dwarf planet by the International Astronomical Union. The smallest known asteroid is 2008 TS26, which is only 3 meters (10 feet) across.
Most asteroids are irregularly shaped; Ceres is one of the few that has a round shape like a planet. The majority of asteroids reflect very little light, so they appear dark when viewed from Earth. However, some asteroids reflect more light and can be quite bright. These include Vesta, Pallas, Iris, and Florence—the four brightest asteroids visible from Earth without binoculars or a telescope.
While most asteroids orbit peacefully between Mars and Jupiter, there are a handful that cross Earth’s orbit on their way around the Sun. These “Earth-crossers” can pose a threat to our planet if they come too close; even small ones could cause serious damage if they hit us! Luckily, we’ve found ways to track these potentially hazardous objects and warn people ahead of time if there’s any chance of impact.