What Is a Comet?
A comet is a large ball of ice, dust, and rock that travels through space. Most comets come from a very cold and far part of our solar system. They move in a long path around the Sun. When a comet gets close to the Sun, the heat makes the ice melt and turn into gas. This gas and dust form a long, bright tail. The tail always points away from the Sun because of the solar wind. Some comet tails are millions of kilometres long.
People on Earth can sometimes see comets in the night sky. A few famous comets come back again and again. Halley's Comet, for example, passes close to Earth about every 75 years. The last time it was visible was in 1986, and it will return in 2061. Long ago, people did not know what comets were. Many were afraid of them. Today, scientists send spacecraft to study comets and learn more about how our solar system was formed.
