The Universe - Dirty Snowballs




The astronomer Frank Whipple created the description of comets as 'dirty snowballs'.

 Comets go around the Sun in a highly elliptical orbit. 

 They can spend many years out in the depths of the solar system before they return to the Sun. 



  Comet Hyakutake (1996)

 As they come closer to the Sun, the warming of the surface causes materials to melt and vapourise, producing the tail. 

 Comet tails can be as long as the distance between the Earth and the Sun.

 The tail always points away from the Sun.

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