Chunks of ice (a dirty snow ball) that orbit the sun far beyond Pluto’s orbit.  As it nears the sun, the ice turns to gas and releases the dust in it making two tails.  The tail of the comet may extend millions of miles into space.  The head of the 1997 Hale-Bopp comet was about 25 miles in diameter.



1.      Scientists believe that comets are made up of material left over from when the Sun and the planets were formed. 

2.      Most comets thought to originate in a huge cloud called the Oort Cloud

3.      Like planets, comets follow elliptical orbit around Sun;  ranging from a few years to several hundred thousand years

4.      about 100 million comets orbit the Sun.

5.      distinct center called a nucleus --. made of frozen water and gases mixed with dust and rocky material.

6.      hazy cloud called a coma surrounds the nucleus – coma and nucleus together form the comet’s head.

7.       When  comet gets close to Sun, part of the ice starts to melt; solar winds then push dust and gas released by the melting ice away from comet, forming the tail.

8.      tail of comet can reach 150 million kilometers in length, but amount of matter it contains can be held in a large bookbag.

9.      comet has no light of its own. – visible on Earth because of reflection of the Sun’s light off the comet.

10. speed of  comet highest near the Sun and decreases as it drifts away;. Comets very far away from our solar system for the large majority of their lifetime

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