Anyone who has seen a comet is probably puzzled as to what exactly they are made of.
At first glance, they look like elongated shooting stars, with tails that stretch out for a long time and often at weird angles.
Comets are, most simply, icy bodies that release dust and orbit the sun. They are composed of several different sections: the nucleus, or more commonly the “black snowball”, which is at the front of the comet and is composed of ice and rocky dust particles; the coma, which is a sort of outer layer of the nucleus which is formed when the ice and rock on the surface of the comet are heated and attach from the nucleus; the dust tail, which is formed by the radiation of the sun repelling the dust particles of the comet; and the ion tail, which is formed by the solar wind produced by the sun repelling charged particles in the coma.
Scientists believe that most comets have a nucleus of about 10 miles across or less. The comas of comets are thought to be significantly larger, with some having a diameter of 1 million miles, and tails even larger with some reaching lengths in excess of 100 million miles.
To Learn More:
Solar Views: What is a Comet?To Learn More:
Hayden Planetarium: What are comets made of?
Kids Cosmos: Asteroid, Comet and Meteor Facts
New Scientist: Instant Expert: Comets and Asteroids