Comets

Comets are small, icy objects that travel around the sun. They are made of ice, dust, and rock. People sometimes call them dirty snowballs. When a comet gets close to the sun, it warms up. The ice turns into gas and forms a big, bright tail. A comet's tail can stretch for millions of miles across the sky.

Parts of a Comet

A comet has three main parts. The center is called the nucleus. It is a hard ball of ice and rock. Around the nucleus is a cloud of gas and dust called the coma. The tail is the long, glowing streak behind the comet. Comets can have two tails. One is made of dust. The other is made of gas. The tails always point away from the sun.

Where Comets Come From

Most comets come from the edge of our solar system. Some come from a faraway place called the Oort Cloud. Others come from the Kuiper Belt, past Neptune. Comets travel in big, stretched-out paths around the sun. Some comets come back every few years. Others take thousands of years to return. Halley's Comet comes back about every 76 years.

Fun Facts

• A comet's tail can be longer than the distance from Earth to the sun.
• The word comet comes from a Greek word that means long-haired star.
• Comets can glow in many colors, like blue, green, and white.

Did You Know?

Some scientists think comets may have brought water and other building blocks of life to Earth a very long time ago.