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Comet Types

A comet---often labeled by astronomers as a "dirty snowball"---is an astronomical body composed of water and dirt that most likely didn't integrate into planets during the formation of the solar system. Like asteroids, comets are described as "leftovers" of the solar system. Two variations of comets exist in astronomy based on their orbit. One is called a "short-period" comet, the other a "long-period" comet.

Short-Period Comets
- The short-period type takes around 200 years or less to complete a single orbit and its orbital path is also less elliptical when compared to long-period comets. These comets are believed to originate from the Kuiper Belt, which makes up the outer edge of our solar system close to Pluto's orbit. The Kuiper Belt is believed to be around 30 to 100 AU (astronomical units) away from the Sun---one astronomical unit being equal to the mean distance between the Earth and the sun.
Long-Period Comets
- A long-period comet takes more than 200 years to complete a single orbit and its orbital path is very elliptical. Astronomers believe that long-period comets come from the "Oort" Cloud, which is located further away than the Kuiper Belt. The Oort Cloud is estimated to be 3,000 to 50,000 AU away from the sun and some astronomers have concluded that it may contain upwards of a trillion comets.
Types of Comet Tails
- Comets display two types of tails when they get near the sun; a gas ion tail and a dust tail. A gas ion tail is straighter and produced when the sun's ultraviolet rays rip gas atom electrons contained in the body of the comet, turning them into ions. These ions are then pushed away by the solar wind, creating a "tail."
  
  On the other hand, dust tails are created by the very small solid particles that move away from the comet's body as they are gently pushed away by sunlight. Dust tails are relatively curved since the sunlight's pressure pushing them is weak.
Asteroids
- An asteroid is commonly mistaken as a comet and vice versa; however, an asteroid has certain characteristics that make it fairly different from a comet. An asteroid is usually made up of carbon, metal and rock, while a comet is made up of ice and dirt. The confusion between the two often occurs when a comet is far away from the sun and its tail is not showing. Asteroids are also concentrated along the Asteroid Belt, which is situated between the orbital path of Mars and Jupiter.

Astronomy