Comets are small, icy celestial bodies that orbit the sun. They are often called “dirty snowballs” because they are made up of dust and ice.
Comets originate in the coldest parts of the solar system, such as the Oort Cloud and Kuiper Belt. As they approach the sun, their ice begins to vaporise, creating a tail of gas and dust that points away from the sun.
There are three main types of comets: short-period comets, long-period comets, and periodic comets. Short-period comets have orbital periods of 200 years or less and generally originate from the Kuiper Belt. Long-period comets have orbital periods greater than 200 years and come from the Oort Cloud. Periodic comets have shorter orbital periods but follow more elliptical orbits; these include Halley’s Comet, which has an orbital period of 76 years.
Here are ten fun facts about comets:
1. The tails of comets always point away from the sun due to solar radiation pressure.
2. Comets can be up to 60 miles wide!
3. When comet nuclei get close enough to the Sun, water starts boiling off them forming what’s called a coma – a giant cloud around comet’s nucleus.
4. A typical comet nucleus is only about 1 kilometre across.
5. Most short period comet nuclei are thought to be fragments left over from collisions between larger objects in our Solar System’s history.
6. The first recorded observation of a comet was by Chinese astronomers in 240 BC.
7. In ancient times people believed that comets were omens of bad news.
8. Some people think that life on Earth may have started when an asteroid or comet crashed into our planet delivering organic molecules.
9. The most famous comet is probably Halley’s Comet which returns every 75 – 76 years.
10. There is currently no way to destroy a comet if it was on course for impact with Earth.