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BOB HIRSHON (host):
How comets kick off. I’m Bob Hirshon and this is Science Update.
Listener Steve Ziemba from Fullerton, California, called with a question about comets:
"The sun I’m told blows particles off the comet, and as they orbit over and over again over millions of years what I want to know is why things like Halley’s comet are still there and have not just been blown apart by the sun."
Well, Steve, be patient. Comet chemist William Jackson from the University of California-Davis says comets only lose a little bit of their mass each time around.
WILLIAM JACKSON (University of California-Davis):
And you’re talking about something that is 30,000 meters in diameter, so it takes a while for you to lose all of it.
In the case of Halley’s comet, about another 400,000 years. If you have a science question, call us at 1-800-why-isit. I’m Bob Hirshon, for AAAS, the science society.