August 8, 2002
Alan MacRobert, Senior Editor
617-864-7360 x151, amacrobert@SkyandTelescope.com
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The Perseid meteor shower, an annual celestial event beloved by millions of skywatchers around the world, returns to the night sky this coming week.
Sky & Telescope magazine predicts that the Perseid shower will reach its peak late Monday night and early Tuesday morning, the night of August 1213. The rate of activity should pick up steam after midnight until the first light of dawn.
Of all the places in the world, Europe appears positioned to get the best show. But North America runs a close second and from here, the previous night (late Sunday evening through early Monday morning) is nearly as good. Best of all, the waxing crescent Moon will set before the prime meteor-watching hours, so this year's Perseids occur in a moonless sky.
You'll need no equipment but your eyes. The darker your sky, the better any artificial light pollution in your sky will reduce the number of meteors that are visible. But even if you live in an urban or suburban area, you have a good chance of seeing at least some meteors. Find a dark spot with a wide-open view of the sky. Bring a reclining lawn chair, insect repellent, and blankets or a sleeping bag; clear August nights can get surprisingly chilly.
"Go out after about 11 p.m. or so, lie back, and watch the stars," says Sky & Telescope senior editor Alan MacRobert. "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, probably straight up. Faint Perseids appear as tiny, quick streaks. Occasional brighter ones may sail across the heavens for several seconds and leave brief trains of glowing smoke.
If you trace each meteor's direction of flight backward far enough across the sky, you'll find that your imaginary line crosses a spot in the constellation Perseus, near Cassiopeia. This is the shower's radiant, the perspective point from which all the Perseids would appear to come if you could see them approaching from interplanetary space. The radiant is low in the north-northeast before midnight and rises higher in the northeast during the early-morning hours.
Don't give up if it's cloudy Monday night. The Perseid shower lasts for about two weeks, with good rates in the predawn hours of August 10th through 15th. Far fewer meteors will appear before midnight, even on the night of the shower's maximum, because the radiant is then quite low in the sky. The radiant is always low or below the horizon for Southern Hemisphere countries like Australia, New Zealand, and South Africa, where few, if any, Perseids can be seen.
The Perseid meteoroids are tiny, sand- to pea-size bits of rocky debris that were shed long ago by Comet Swift-Tuttle. This comet, like others, is slowly disintegrating as it orbits the Sun. Over the centuries, its crumbly remains have spread all along its orbit to form a sparse "river of rubble" hundreds of millions of miles long.
Earth's own path around the Sun carries us through this stream of particles every mid-August. The particles, or meteoroids, are traveling 37 miles per second with respect to Earth at the place where we encounter them. So when one of them strikes the upper atmosphere (about 50 to 80 miles up), it creates a quick, white-hot streak of superheated air.
More about the Perseid meteors and how to watch and photograph them appears in the August issue of Sky & Telescope magazine and online in the articles listed at the end of this press release.
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