What is Comets. Comets are small celestial bodies that orbit the Sun. They have a nucleus center and may or may not have a tail. They orbit the Sun at very long intervals in highly elliptical orbits. They pass by the Earth on a cyclical schedule.
Comets have a central nucleus called coma. This coma is composed of rock, dust and ice. As the comet gets closer to the Sun, the ice melts and this creates a lot of dust and debris. As the pressure of the sun increases, the solar wind pushes the dust and debris into a beautiful comet tail. The sun illuminates the tail and we can view the comet from Earth.
Before the invention of telescopes, comets would appear out of nowhere. It seemed like they would illuminate themselves all of a sudden, not unlike the recent comet, Comet Holmes. Comet Holmes saw a flareup in just a few days that made it visible on Earth with the naked eye. Before, it had only been visible as a faint image in a telescope.
Now scientists are able to see and discover comets that would otherwise not be visible on Earth. Because of the cyclical nature of comets, some comets may only appear every several hundred years. There's always a chance for an amateur with a telescope to discover a never before seen comet, much like the discovery of the Hale-Bopp Comet in 1996.
Comets are believed to originate in the Oort Cloud. The Oort Cloud is located in the farthest reaches of our solar system and is nearly 3 light years in size. It is in the Oort Cloud that comets originate and return to. Because of this huge distance and the huge size of the Oort Cloud, Comets come at regular intervals of hundreds of years. This is compounded by the highly elliptical orbits of Comets. For example, the most famous comet, Haley's Comet comes every 76 years. Unfortunately, it's the only naked eye viewable comet that comes so often.
Comets are the source of folklore and beauty in our sky. A comet gives us a chance to really see the beauty in astronomy.