Dusk and dawn delights

Posted by Rich Talcott
on Thursday, January 11, 2007

The big news in the observing world this past week has been the remarkable brightness of Comet C/2006 P1 (McNaught). It has now reached magnitude -2 — as bright as the planet Jupiter — and makes an impressive sight shortly after sunset.

Comet C/2006 P1 (McNaught) hangs low in evening twilight, just above
some encroaching clouds, from Astronomy’s headquarters in Waukesha,
Wisconsin. Ernie Mastroianni

The comet took most astronomers by surprise. It was a 17th-magnitude object August 7, when Robert McNaught of Australia's Siding Spring Observatory discovered the faint smudge, and it brightened slowly over the next few months. In October, it barely mustered 13th magnitude, and it reached only 10th magnitude in November. It started to exceed expectations during December, and became visible to the naked eye by Christmas.

Yet Comet C/2006 P1 saved its best for this week. On both Tuesday and Wednesday evenings, the skies above Wisconsin were clear, and the comet put on a great show. Several of us saw the comet's head and broad dust tail without optical aid — even in bright twilight — but the best view came through binoculars. All in all, it has to rank as the best comet I've seen since Hale-Bopp a decade ago. (Unfortunately, the comet will sink into the Sun's glare in the next few days, and be lost to Northern Hemisphere observers.)

At least we had a little warning about Comet C/2006 P1. An equally spectacular and totally unexpected scene greeted me before sunrise Wednesday morning. As I was driving to work, I saw a brilliant Sun pillar rising from the horizon. At its best, it stretched a third of the way to the zenith and shone brighter than any Sun pillar I had even seen. A bright and colorful "Sun dog" — light refracting through ice crystals at a distance of 22° from the Sun — added to the glorious scene.

Sun pillars — sunlight reflecting off six-sided ice crystals in thin, high-level clouds — particularly fascinate me. Over the past several years, Egyptologist Patricia Gary and I have researched the role Sun pillars may have played in the development of Egypt's earliest art and architecture. (See our article, "Stargazing in ancient Egypt," in the June 2006 issue.) So, Wednesday's dazzling Sun pillar hit me in both a scientific and an aesthetic sense.

The week's double celestial delights also drove home what should be every observer's mantra: Although it pays to keep abreast of what's going on the sky, always be alert for the unexpected.

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