August 8, 2007
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More information for the general public is available at SkyandTelescope.com/Perseids.
The Perseid meteor shower, an annual celestial event beloved by millions of skywatchers around the world, returns to the night sky this coming weekend. And with a new Moon occurring at the same time, skywatchers won't have bright moonlight spoiling the view.
Sky & Telescope magazine predicts that the Perseid shower will reach its peak late on Sunday night, August 12th. The rate of activity should pick up after midnight until the first light of dawn. "The combination of a moonless night, together with a peak timed to favor North America, means that conditions for this year's display will be ideal," notes Sky & Telescope senior editor Alan MacRobert.
To enjoy the Perseids, you'll need no equipment other than your eyes. Find a dark spot with a wide-open view of the sky. Bring a reclining lawn chair or a blanket so you can look skyward without neck strain. The later you can stay up, the more meteors you're likely to see. "Go out after about 11 or midnight or so, lie back, and gaze up at the stars," MacRobert suggests. "Relax, be patient, and let your eyes adapt to the dark. With a little luck you'll see a 'shooting star' every couple of minutes on average."
Perseids can appear anywhere and everywhere in the sky. So the best direction to watch is wherever your sky is darkest. Faint Perseids appear as tiny, quick streaks. Occasional brighter ones may sail across the heavens for several seconds and leave a brief train of glowing smoke.
Don't give up if it's cloudy Sunday night. The shower lasts for about two weeks, with satisfying displays in the predawn hours of August 10th through 15th.
HOW AND WHY
The meteors are caused by tiny, sand- to pea-size bits of dusty debris slamming into Earth's upper atmosphere about 80 miles up. Each particle zips in at 37 miles per second, creating a quick, white-hot streak of superheated air. (Note: The nuggets in Grape Nuts cereal are a close match to the estimated size, color, and texture of typical particles.)
These particles were shed long ago by Comet Swift-Tuttle and are distributed all along the comet's orbit around the Sun. Earth passes through this tenuous "river of rubble" every year in mid-August.
If you trace each meteor's direction of flight backward across the sky, you'll find that all the Perseid meteors seem to radiate outward from a spot in the constellation Perseus, near Cassiopeia. This radiant, a perspective effect, is low in the north-northeast before midnight and rises higher in the sky during the early-morning hours. Few if any Perseids can ever be seen from Southern Hemisphere countries like Australia, where this radiant is always near or below the horizon.
More about the Perseids and how to watch them appears in the August 2007 issue of Sky & Telescope magazine and at the magazine's website.
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