The Sciences

Comet Holmes

Cosmic VarianceBy John ConwayNov 8, 2007 5:17 PM


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We started to get a naked-eye view of Comet 17P/Holmes last week, after it underwent a transformation in which it apparently ejected a huge cloud of gas, much of which is CN and C2, and NH2 molecules, and which are fluorescing. Unless you knew it, you would think it's another star in the constellation Perseus, about half way between Cassiopeia and the Pleiades in the northeast sky in the evening. With no moon now and clear skies in Northern California, I got this shot with my little Canon Rebel on a tripod (with a 300 mm Tamron lens, 10 sec exposure at f/4.5):

Looking at it with binoculars, it it hard to resist the urge to try to focus it! But it's just a big fuzzy ball... The comet is on its way out of the inner solar system, having made perihelion last spring. The gas cloud has expanded to 70% of the diameter of the sun.

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