Asteroids are small rocky objects that orbit the sun. Although asteroids orbit the sun like planets, they are much smaller than planets.
There are many asteroids in our solar system. Most of them live in the asteroid belt – a region between the orbits of Mars and Jupiter.
Asteroids hang in other places, too. For example, some asteroids are in the orbital path of the planets. This means that the asteroid and the planet follow the same path around the sun. Earth and some other planets have asteroids like this. But do not worry, do not collide!
Where do asteroids come from?
Asteroids are left over from the formation of our solar system. Our solar system began about 4.6 billion years ago when a large cloud of gas and dust collapsed. When this happened, most of the material fell to the center of the cloud and formed the sun
Some of the dusts that condensed in the cloud became planets. The asteroid belt objects never had the opportunity to be incorporated into the planets. They are remnants of that distant time when planets formed.
Are all asteroids the same?
No way! Because asteroids form in different places at different distances from the sun, no two asteroids are the same. Here are some ways they differ:
Asteroids are not round like planets. They have jagged and irregular shapes.
Some asteroids are hundreds of kilometers in diameter, but many more are as small as pebbles.
Most asteroids are made of different types of rocks, but some have clays or metals, such as nickel and iron.
Since asteroids form at the same time as other objects in our solar system, these space rocks can give scientists a lot of information about the history of planets and the sun. Scientists can learn about asteroids by studying meteorites: small fragments of asteroids that have flown through our atmosphere and landed on Earth's surface.
Several NASA space missions have also flown and observed asteroids. The NEED Shoemaker spacecraft landed on Eros, an asteroid near Earth, in 2001. Then, the Dawn spacecraft traveled to the asteroid belt in 2011 to orbit and study the second largest object there, Vesta. Vesta is as big as a small planet. In 2012 Dawn left Vesta and went into orbit around the largest object in the asteroid belt, the dwarf planet Ceres.
In 2016, NASA launched the OSIRIS-REx spacecraft to study an asteroid near Earth called Bennu and take a sample of the asteroid to Earth!