Did you know that there are really millions of planets orbiting the Sun? Apart from nine “proper” planets, there are a few million, minor ones, called asteroids. These are different chunks of rock, which range from specks of dust to those which are a few kilometres across. Most of them travel in an orbit between Mars and Jupiter called the asteroid belt. Others follow different orbits. In the 18th century, astronomers were convinced that a missing world existed between Mars and Jupiter. A search was mounted and the first asteroid, Ceres, was discovered by an Italian astronomer Giuseppe Piazzi in 1801. Today, over 5000 have been catalogued.
Most asteroids journey around the Sun in the asteroid belt. Others are in smaller groups with different orbits. A group named the Trojans travel along Jupiter’s path- some in front of the planet and some behind. A group called the Apollo …show more content…
Here, the ice boils away to form an enormous head and a long tail. As a comet travels, it sheds bits of itself; from Earth, these are seen as showers of light called meteors. Astronomers would love to get a hold of a comet sample because it would be a piece of evidence from the birth of the Solar System.
Comets have been observed and recorded for thousands of years but they have not always been understood. They were once called “hairy stars” and their sudden appearances made superstitious people regard them bad omens.
People could only guess what a comet’s nucleus was like until a space probe called Giotto flew past the nucleus of Comet Halley in 1986. It sent back photographs showing a nucleus that looks an icy, rock potato and measures 16×8km (10×5 miles). This was the first conformation that comets are giant, dirty snowballs (predicted by an American called Fred Whipple in