Asteroids

Apart from the Sun and planets, the solar system contains lots of other objects. These range from the large moons of the planets to the fine dust that causes meteors in the Earth's atmosphere. Asteroids are an especially important part of this solar system 'junk'.

It is not known why all the material that is now in the asteroids didn't originally clump together to form another rocky planet. Did the gravity from nearby Jupiter stop it collecting together? Did another planet form in the expected place and did Jupiter's gravity then break this young planet into all the pieces we see today? Astronomers are still searching for the answer.

Most asteroids are found in the 'main belt' and orbit the Sun at a distance of about 2.8 AU. This was one of the predictions of Bode's Law.

Some asteroids that are not in orbits in the main asteroid belt are of more interest to us here on Earth. They are the so-called Near-Earth Asteroids. They have orbits around the Sun that sometimes take them very close to the Earth - possibly sometimes just too close. Could a collision with such an object have created an explosion that led to the death of the dinosaurs? Nowadays, some telescopes are dedicated to finding and tracking these objects - if one is going to hit the Earth, we want to see it coming and to have time to panic!