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Introduction to Comets
Comets are beautiful small objects that exist in space mostly made up of water, dust and small stones. Known as ‘dirty snowballs,’, they have a peculiarity of displaying one characteristic as they near the sun and this is some of the best shows that can be seen from earth. Knowledge about comets is vital to improve the knowledge of the early solar system and about the sources of water on earth.
Composition of Comets
- Nucleus: The nucleus is the dense and centrally concentrated body of specific size that varies from a few kilometers across. It is a combination of the very cold and frozen water, carbon dioxide, methane, ammonia, dusts and small rocks particles. This composition can best be described as representative of the basics that came together to create the solar system.
- Coma: Solar heating of the comet nuclei takes place when a comet is within the Sun’s influence; this heating compels the ice to change directly to gas. The concentration of gas and dust around the nucleus forms a second shell called the coma which can be hundreds of times larger than its core. Coma obtains an extremely important position in forming the comet’s tail.
- Tails: Comets usually create two distinct tails, a dust tail and an ion tail. The dust tail results from tiny fragments expelled from the C/ atmosphere by pressure from solar light rays and heat, while the ion tail is made of charged gas particles affected by the force of solar wind. As a result both tails always fit away from the sun.
Types of Comets
- Short-Period Comets: The above comets have short orbital periods by a range of less than 200 years on average. They’re thought to come from the Kuiper Belt, an area beyond Neptune that is composed of icy objects. Comet Encke is typical of objects that orbit with an average period of about 3.3 years.
- Long-Period Comets: These comets have orbits that may take thousands to millions of earth years to be complete. It is believed that they start from the Oort Cloud – a spherical formation outside the Solar System, consisting of icy objects. These comets can be altered to inner solar system orbits by close encounter with other stars.
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