Labels:text | screenshot OCR: COMETS MOST OF THE BILLIONS of comets in MELTDOWN Dust jet | the Solar System exist in its outer When the nucleus nears the reaches, but some follow orbits that bring Sun, its ices vaporize and them close to the Sun, and occasionally jets of water vapor one of these makes a striking appearance spurt from the nucleus. in the night sky. Each comet has an icy, dusty nucleus (known as a "dirty snowball") about 20 km (12 miles) across. Nucleus When the nucleus vaporizes as it nears the Sun, a bright head and long tail form. COMET WEST, 1976 Gas jet This comet has two tails: a straight, blue Coma gas tail and a curved, yellow dust tail. COMET TAILS SEE THE OPIK-OORT HALLEY'S COMET THE TUNGUSKA FACT NEXT ALSO CLOUD COMET SHOEMAKER-LEVY EXPLOSION FILE
