Not too long ago, many people thought that comets were a sign that something terrible was about to happen. People didn't understand about how objects in the sky moved, so the sight of a comet must have been very scary.

Now we know that comets are lumps of ice and dust that come flying into the solar system from deep space, and that some comets make repeated trips. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long.

Unfortunately, we don't get to see comets very frequently. In 1985-1986, a spacecraft called Giotto visited the most famous comet of all, Halley's comet. In 1994, a comet named Shoemaker-Levy, ran into Jupiter!

In 1996 and 1997, we could see comet Hyakutake, and comet Hale-Bopp from Earth. Hale-Bopp was one of the brightest comets ever seen from Earth. Comet Linear was discovered in 1999 and came closest to the Sun in July 2000. The Stardust spacecraft flew by Comet Wild 2 in January 2004, collecting samples of the comet to return to Earth. The newest comet mission is Rosetta and it will land on a comet named Churyumov-Gerasimenko

Now scientists have identified a class of comets known as small comets (though they originally were just called snowballs from space!).

How would you like build your own comet? Now you can, with our interactive comet animation. Check it out!