東東 (就是 Nita 的金童小冤家啦！) 有一個天文望遠鏡~~~
http://news.yahoo.com/s/ap/20071103/ap_on_sc/brighter_cometSat Nov 3, 12:57 AM ET
KNOXVILLE, Tenn. - A comet that has unexpectedly brightened in the
past couple of weeks and now is visible to the naked eye is attracting
professional and amateur interest.
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Paul Lewis, director of astronomy outreach at the University of
Tennessee, is drawing students to the roof of Nielsen Physics
Building for special viewings of Comet 17P/Holmes.
The comet is exploding and its coma, a cloud of gas and dust
illuminated by the sun, has grown to be bigger than the planet Jupiter.
The comet lacks the tail usually associated with such celestial bodies
but can be seen in the northern sky, in the constellation Perseus, as a
fuzzy spot of light about as bright as the stars in the Big Dipper.
”This is truly a celestial surprise,” Lewis said. ”Absolutely amazing.”
Until Oct. 23, the comet had been visible to modern astronomers only
with a telescope, but that night it suddenly erupted and expanded.
A similar burst in 1892 led to the comet’s discovery by Edwin Holmes.
”This is a once-in-a-lifetime event to witness, along the lines of when
Comet Shoemaker-Levy 9 smashed into Jupiter back in 1994,” Lewis
said.
Scientists speculate the comet has exploded because there are
sinkholes in its nucleus, giving it a honeycomb-like structure. The
collapse exposed comet ice to the sun, which transformed the ice into
gas.
”What comets do when they are near the sun is very unpredictable,”
Lewis said. ”We expect to see a coma cloud and a tail, but this is
more like an explosion, and we are seeing the bubble of gas and dust as
it expands away from the center of the blast.”
Experts aren’t sure how long the comet’s show will last, but estimate it
could be weeks — if not months. Using a telescope or binoculars help
bring the comet’s details into view, they said.
