Friday, November 9

A comet explodes

Saturday 3 November Last night we found the comet. Cool. There it was, just below Cassiopeia, like Sky & Telescope said. Looking like a fuzzy ball in the binoculars. After that and knowing where it was, I saw it with naked eyes well enough to direct Lanney's binocular search.

Comet 17P/Holmes, November 2, 2007, 1:53 AM MDT (7:53 UT) Photo courtesy of Ginger Mayfield and Wikipedia.

Lanney and I never would have seen it with binoculars a little over a week ago, when it was a dim magnitude 17 star. In just a few hours on 24 October, the comet went from that barest glimmer to a 2.5 magnitude star. It exploded! Why?

"What comets do when they are near the sun is very unpredictable," says Paul Lewis, director of astronomy outreach at the University of Tennessee. "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. Absolutely amazing."

The coma cloud of Comet 17P/Holmes is now more than 600,000 miles across, bigger than the planet Jupiter and approaching the diameter of the Sun.

Further Reading

Astronomers dazzled at comet's brightness,

17P/Holmes, Wikipedia

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