An artist’s illustration of asteroids, or near-Earth objects. CREDIT: ESA - P.Carril
- Ceres is the largest known asteroid at approximately 950 km (590 miles) in diameter. It’s so large that it’s also classified as a dwarf planet.
- Asteroids are too small to be spherical in shape. Instead, they are usually ellipsoids, but some are dumbbell-shaped, and others form even stranger shapes.
- Asteroids are not always solid rocks. Often, they’re more like piles of rubble held loosely together by their collective gravity.
- Most asteroids tend to be either rocky in nature or more metallic. Metal-heavy asteroids, even small ones, can slice through Earth’s atmosphere without much impediment and crash into the surface. Stony asteroids are much more likely to vaporize in the atmosphere or, if they are very large, explode near the surface.
- Once they enter Earth’s atmosphere, asteroids are called meteors, and if they survive to the surface, they are termed meteorites.
- If all of the asteroids in the belt were combined, they would form a body less than 1500 km (932 miles) in diameter or less than half the size of the moon.