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Celestial bodies consisting of a central frozen mass, frozen gas and dust that loop around the sun in long, elliptical orbits are known as comets. When comets approach the sun they begin to glow as they warm up releasing gas and dust that form long tails behind them. These tails can stretch for millions of miles and are know to point away from the sun no matter what direction the comet is moving. The most famous of comets, which is seen in our atmosphere every 76 years, is Halley's Comet. But every year new comets appear in our sky even though most are not bright enough to be seen without a telescope or binoculars. It is believed that far beyond Pluto's orbit there is a cloud of ice chunks and dust which contains comets. Gravity from nearby stars are believed to cause the comets to fall toward the sun where Jupiters gravity moves it into a closed orbit. Scientist interest in comets arise from the material brought to us from the extreme depths of our solar system.
Large pieces of metal or rock that enters the earths atmosphere producing a streak of light are known as meteors. Some meteors appear in the sky much brighter than any planet. These are called fireballs. When the friction within earths atmosphere causes a meteor which is falling at a speed of 45 miles per second to burn up with a sudden streak of light this is often what we would call a shooting star. Many of the meteors we see are simply comet dust. When the earth is traveling through a comets orbit at the same time each year, dust spreading out from that comets orbit creates a meteorite shower. If the meteor hits the earth it becomes a meteorite. Hundreds of meteorites enter the earths atmosphere each year. The majority are small and land in oceans or unpopulated areas. Meteorites appear to be ordinary stones but most are made of iron and nickel. The dark crust that forms on a meteorite is caused by its fiery passage through earths atmosphere. When cut open and etched with acid the exposed surface will many times take on a beautiful pattern.
The largest known meteorite to ever hit the earth landed at Grootfontein in Nambia, South Africa and weighed 60 metric tons. In the United States a huge iron meteorite that struck the Arizona desert about 20,000 years ago was destroyed by the impact but left a crater that measures .74 miles. On January 3, 1970 a 21.6 pound meteorite landed in Oklahoma and was recovered. A meteorite weighing 33 pounds was discovered in Nueva Lean, Mexico and more recently a small meteorite that fell in Connecticut was recovered by a young girl and sent to scientist at the University of California at Los Angeles.