ACM - Comets LESSON
Comets
Have you ever seen a shooting star or falling star before? Would you be surprised to learn that they are not in fact stars that are falling? Before we begin learning about comets, complete the discussion on falling stars to learn about this misconception.
Comets are composed of frozen gasses, rock, and dust. When a comet gets close enough to the Sun, the dust and frozen gases heat up and will emit out behind the comet. This creates a "tail" that stretches away from the Sun.
Anatomy of a Comet
Each comet has a tiny frozen part, called a nucleus, often no larger than a few kilometers across. The nucleus contains icy chunks, frozen gases with bits of embedded dust. A comet warms up as it nears the Sun and develops an atmosphere, or coma. The Sun's heat causes the comet's ices to change to gases so the coma gets larger. The coma may extend hundreds of thousands of kilometers. The pressure of sunlight and high-speed solar particles (solar wind) can blow the coma dust and gas away from the Sun, sometimes forming a long, bright tail. Comets actually have two tails - a dust tail and an ion (gas) tail.
| Components of a Comet | Comet Components |
|---|---|
Halley's Comet
Halley's Comet was named after English astronomer Edmond Halley. He discovered it after examining reports of a comet approaching Earth in the years 1531, 1607, and 1682. Based off the observations and research in his day, he concluded that these all were in fact the same comet. He predicted that the comet would return again in 1758. Halley's Comet is known as a periodic comet because it returns to a general location over a predictable period of time. Halley did not live to see the comet return in 1758 but it was named after him because of his discovery. Further research concluded that Halley's Comet orbits the Sun.
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