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Old 02-November-2007, 04:33 AM
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Wicked Lad Wicked Lad is offline
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Join Date: Aug 2007
Location: Near Philadelphia, Pennsylvania, USA
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So I brought the exploding comet to my 13-year-old stepdaughter's attention by e-mail, and she wanted to know why it's exploding. I did a quick Web search and wrote back:
Quote:
It appears no one is sure why comet 17P/Holmes is brightening like this. I found a Web site that says it "could be due to a sudden exposure of fresh cometary ice or even the breakup of the comet nucleus. " I think the "exposure of fresh cometary ice" refers to the fact that most comets are covered with dust. If an area of dust got removed somehow, maybe the solar wind would blast away at the ice, and the ice would reflect a lot of sunlight.
Tonight she replies:
Quote:
That could be it.... But would the ice really be that reflective? And is this comet very big? Why would the nucleus break up? I'm wondering how scientists know this....
I'm so proud of that kid. All excellent questions, and such economy of expression. And the only question I think I can answer is about the (approximate) size of the comet.

I have to take the blame for that last bit about "how scientists know this." I made her tatoo "How do you know?" on her forehead backward so she sees it every time she looks in the mirror. Okay, not really. But I've told her over and over she needs to ask that question. She needs to ask it a lot.

Anyway, I've been reading what I can find about what would explain the "outburst." I think I have to deploy that other sentence indispensible in scientific inquiry: "We just don't know."

What about her other question? Is ice really that reflective? If not, what's likely to cause the glow? And BTW, is it safe to assume it would be water ice?
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