dipper@utastro.UUCP (Debbie Byrd) (12/29/85)
A very bright meteor is called a fireball. We'll talk about the December fireballs -- right ater this. December 29: December Fireballs Around this date -- until the end of this week -- lucky observers will see some exceptionally bright meteors called December fireballs. A fireball is different from an ordinary meteor simply because it's brighter. Fireballs may be about as bright as the brightest starlike object ever seen in the night sky -- the planet Venus. But a fireball isn't just a point of light. It's a streak of light that can illuminate the entire sky --explode in a flash -- or leave a smokey trail. Fireballs are also called bolides, from a Greek word meaning "to throw." They're not really balls of fire, of course, but more likely balls of ice or rock which have been adrift in the space inside our solar system since its early history. They become fireballs when they vaporize on their encounter with Earth's atmosphere -- and they're caused to vaporize by friction with the air -- which produces heat for just the same reason that your two hands get hot when you rub them together. The December fireballs are really more of a southern hemisphere phenomena, since they're seen to radiate from a point in the south celestial sphere. They've been observed since 1974 in New Zealand -- and probably originate in a cluster of chunks of debris whose orbit around the sun coincides around near the end of December with that of the Earth. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin