What is a Comet?
A comet is a small astral body, similar in construction to a planet. A comet may have an unusual orbit, which may at times bring the comet close to the sun and make it visible to the naked eye, or through relatively low strength telescopes. When such a comet can be viewed it is usually noted as having a tail, made of gasses, which early astronomers often mistook for a shooting star.
Most observable comets in our solar system derive from the Oort Cloud, a hypothesized cloud made up of leavings from the sun. These materials form comets, which orbit the sun because are then affected by the gravitational pull of the sun and other planets. While passing by individual planets, the comet may be affected by the gravitational forces of the planets, thus causing an elliptical or oval-type orbit.
Usually, people on earth see a comet when the comet passes in between earth and the sun. It is thought that the comet and its tail, sometimes called the coma and tail, reflect the light of the sun, enhancing visibility. Since comets may orbit the sun in such strange patterns, people may only see the passage of one comet in a lifetime.
In fact, comets are usually classed by the length of time it takes them to orbit the sun. A short period comet takes about 200 years or less to make a full trip around the sun. A long period comet may take far more than 200 years to complete a trip.
For example Halley’s Comet can be viewed on earth about every 75 years. This marks it as a short period comet. Its last sight on earth was in 1986, and it is expected to be seen again in 2061.
A planet may capture a comet and the result can cause significant damage to the comet. Such a gravitational capture may result in the comet breaking into many small pieces, and these smaller pieces can then break off from the comet and hit the capturing planet. Comet Shoemaker-Levy 9, was observed as broken in 1993, and astronomers were able to witness it hitting the atmosphere of Jupiter in 1994.
Most often people looking at the night sky may think that they see “falling stars” which are actually meteors or comets. There are thousands of tiny comets that do not attract much interest. The once in a lifetime comet like Halley’s are often thought of as exciting, since most people will only see them with the naked eye once.
Written by Tricia Ellis-Christensen
