By: Hannah Harris and Lauren B. Comets

Facts Comets, like asteroids are small celestial bodies that orbit the sun. However, unlike asteroids comets are made mostly of frozen ammonia, methane or water, and contain only small amounts of rocky material. As result of this comets have been given the nickname of “dirty snowballs”.

Comet Hartley 2 On October 20th, Comet Hartley 2 will pass just over 11 miles (18 million km) from Earth. During October it should be easily visible in small telescopes, binoculars and even your own two eyes.

Biggest Comet in History The Great Comet of 2007 made an even bigger impression on the solar system than anyone realized, according to a new study that measured the size of the comet's wake. In January 2007 people around the world watched comet McNaughton streak across the sky. It was the brightest comet seen since 1965 and, in some places, was visible to the naked eye in broad daylight. (See a picture of comet McNaughton over New Zealand.) The visible tail was about 35 degrees long, or roughly the same apparent size as 70 full moons lined up in the night sky. By chance, the European Space Agency's Ulysses spacecraft plowed through the width of the comet's tail in February 2007.

Our Sources Comet Facts: Interesting Facts about Comets - The Planets Hartley 2: The 'Weird' Comet - Space.com National Geographic

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