A comet is an icy body made up of gases and dust. When it passes close to the sun, the gases produce a visible atmosphere. Sometimes, the body also produces a visible tail. Like planets, comets are in an orbit around the sun. In 1994, comet Shoemaker-Levy collided with Jupiter.
Photo: Comet Shoemaker-Levy breaking up over the planet Jupiter (Creative Commons: NASA).
Comets: Properties and Behavior
Comets are made up of an ice and dust core. The icy material is mostly water. However, it may also contain solid carbon dioxide, methane, and ammonia. The core can be up to 16 kilometers in diameter.
As comets approach the sun, the icy material is turned into a gas. The gas forms a coma (a cloud of gases). Solar radiation also produces a tail that points away from the sun. These tails can be up to 160 million kilometers long.
Comets move in an elliptical orbit around the sun. At one point in the orbit, the comet approaches close to the sun. At the other extreme, the comet may swing far beyond the orbit of Pluto. Periodic comets have an orbit less than 200 years. Other comets have orbits that are well over 1000 years. The famous Halley’s Comet has an orbit of 76 years.
Comet Smashing into Jupiter
In 1994, the comet Shoemaker-Levy collided with the planet Jupiter. It is now thought that Jupiter helps protect the inner planets from similar collisions.
If such a comet were to strike the earth, it would cause planet wide destruction. In times past, a comet striking the earth may have caused the extinction of life. The damage caused from the collision would include such things as a huge explosion, tsunamis, fires, etc. In addition, the cloud of dust would alter the earth’s climate for many years.
Video: Comet Striking Jupiter (source: YouTube).
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