A comet is a small object made mostly of ice, dust, gas and rock. They are often called dirty snowballs! The largest of comets are just a few kilometres across. When they orbit close enough to Earth we see them as brilliant bright bodies passing through the sky.
- Comets come from the Kuiper belt and the Oort Cloud. These areas of space are way out in the solar system far away from the Sun. The Oort cloud is so far away we have never even seen it! The comets visible from Earth are most likely ones that came from the closer Kuiper belt which is near Pluto.
- There are millions of comets and they are all orbiting the Sun. Most take less that two hundred of years to do so and others travel much slower, potentially taking millions of years to complete an orbit.
- Comets spend most of their years in the Kuiper belt and Oort cloud. Every now and again two comets can crash into one another. When this happened they often change direction, this can throw them out towards the inner solar system.
- When a comet approaches the inner planets it is warmed by the Sun. When this happens it begins to melt and throws out dust and gas. This creates a head and the tail. The tail is the part of the comet we see in the sky. The tail always points away from the Sun. This means that sometimes the tail is behind the comet and sometimes it it infront. It all depends on whether the comet is travelling towards or away from the Sun.
- Travelling through a comet’s tail is not dangerous. In fact Earth even passes through them. When this happens we see a meteor shower!
- The word comet comes from the Greek word Kometes meaning long hair. This is because of how a comet’s tail can look like long flowing locks of hair.
- Like asteroids, comets are leftovers from the formation of the Solar System. We don’t know an awful lot about them at this point but scientists believe they may hold clues to how the Solar System came to be.
- The most famous comet of all time is Halley’s comet. Halley is a periodic comet and is visible from Earth every 76 years and has been for centuries. It made its last appearance in 1986. Other famous comets include the Hale-Bopp Comet, Donati’s comet and the Shoemaker Levy 9 Comet.