Observing Comet
Hale -Bopp from Southern Ontario
A comet is a frozen chunk of icy material consisting of frozen gases plus particles of dust. Comets are sometimes referred to as "dirty snowballs" and the solid part is typically a few kilometers in diameter. Large numbers of comets exist in the outer reaches of our solar system in two main groups. Long-period comets reside in a spherical shell, called the Oort cloud, at very great distances between 1,000 to 30,000 times further from the Sun than the Earth. Short- period comets are found in a disk that lies between 30 to 50 times the Earth's distance from the Sun.
When far from the Sun a comet doesn't glow or have a tail. As it approaches the Sun it absorbs sunlight and begins to heat up. The heat causes gases to escape from the surface, forming a spherical cloud called the coma. The gases in the coma consist mostly of water, carbon dioxide, carbon monoxide and small amounts of ammonia, methane and hydrogen. Ultraviolet light from the Sun causes these gases to glow. As the comet nears the Sun, solar radiation and the solar wind force some of the gas in the coma away from the comet to form a tail. Comet tails have been known to stretch up to 100 million Kilometres. Dust particles are less strongly affected by the Sun and form a separate tail in a direction that is partially influenced by their orbital motion and therefore does not point directly away from the Sun.
Hamilton Amateur Astronomers
P.O. BOX 65578
DUNDAS, ONTARIO
CANADA L9H 6Y6
By:
Grant Dixon
Ann Tekatch
Stewart Attlesey