Comets, asteroids and meteors

Comets

Comets are large snowball like heavenly bodies which revolve around the sun in elliptical path. The comets are made up of rocks and dust which are held together by ice and frozen gases. Comets are formed in the distant regions of solar system beyond Pluto. During their revolution, when a comet passes near to the sun, its crust starts to melt due to high temperature of sun and it produces a long glowing tail. The tail of a comet can be several kilometers long and always points away from the sun. Usually, the period of revolution of comets around the sun is very large. For example,Halley’s comet has a return period of 76 years. Thus, Halley’s comet can be seen after every 76 years. Its last visit was in 1986.

Asteroids

Asteroids are minor planets which are present in asteroid belt between the orbits of Mars and Jupiter. There are about 1 million asteroids in the solar system. The size of asteroids varies in the range of 10 meters to about 950 km. in diameter. The biggest asteroid called Ceres has a diameter of about 940 km.

Meteors and Meteorites

Meteors are the small pieces of rocks and metals from space that enter the atmosphere of earth with high speed. When meteors enter the atmosphere of earth they burn up completely before reaching the surface of earth. This happens due to production of large amount of heat due to resistance of air. Due to burning of meteors, they appear as a bright streak of light in the sky. The meteors are also called as shooting stars.

Sometimes the meteors are very big in size. So, such big meteors do not burn completely and collide with the earth. Such meteors that actually collide with the earth are called meteorites.

Differences between a Star and a Meteor or Shooting Star

Test Your Understanding and Answer These Questions:

1. What are comets?
2. Give some names of comets?
3. What are asteroids?
4. What are differences between comets and asteroids?
5. What are meteors?
6. What are meteorites?