Some "Out of The Word" Stuff"
Perseid Meteor Shower Begins Slow Crawl to Aug. 12 Peak
By Joe Rao
Special to SPACE.com
And Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
25 July 2002
The annual Perseid meteor shower has begun in modest fashion and will soon start building toward a peak Aug. 12, when as many as 60 or more shooting stars could be visible each hour from the Northern Hemisphere.
The Perseids are not as spectacular as the November Leonids, but they are dependable. Nearly every year they generate a shooting star per minute at their peak.
Weather permitting, this will be a good year to look for the Perseids, because the Moon will be near its new phase, leaving the skies at their darkest. The best viewing times run from Aug. 11 through Aug. 13.
For city dwellers whose view is hampered by bright lights, only the brightest meteors can be seen, so a trip to the country is the only way to get the full effect of the Perseids
Perseids are tiny things, ranging in size from sand grains to peas. The material was shed long ago by a comet named Swift-Tuttle. This comet, like all others that pass through the inner solar system on their orbits around the Sun, is slowly disintegrating. Over the centuries, the comet’s crumbly remains have spread all along its orbit to form a moving river of rubble millions of miles wide and hundreds of millions of miles long.
Earth’s orbit carries it through this stream every August. When a particle strikes the planet’s upper atmosphere, air friction vaporizes it in a quick, white-hot streak.
Technically, the peak occurs in the afternoon of Aug. 12 in North America. Meteors can only be seen at night, however. The best views will come late Sunday, Aug. 11 into the early hours of Monday. The shower should remain strong Monday night and into dawn on Tuesday, Aug. 13.
"Rates from rural observing sites should approach and perhaps even surpass 60 Perseids per hour during the last few hours before dawn on Aug. 12," said Robert Lunsford of the American Meteor Society.
For Europe, the peak comes near or soon after midnight on Aug. 13. Few Perseids are ever visible from the Southern Hemisphere.
The Perseids are considered active from about July 25 through Aug. 18, though hourly rates usually do not rise above 10 until about Aug. 8. Rates fall off much more rapidly after the peak, dropping again to below 10 per hour after about Aug. 14.
Early morning hours are best, astronomers say, because the part of Earth on which you stand is then facing the oncoming debris as the planet plunges through space on its orbit around the Sun. Experts suggest going out around 2 a.m. and staying until dawn breaks. Allow at least 15 minutes for your eyes to adjust to the darkness. Then face northeast, because Perseids radiate from a point in the constellation Perseus, which is high in the northeast during pre-dawn hours.
Since this year's best viewing is on a Monday morning, Lunsford offers strategies for working people.
"I would suggest watching during the last hour or two before dawn," Lunsford advises. "This will allow you to see the most Perseid activity from your particular location."
He also recommends doing some practice observing beginning around Aug. 8. By then, the Moon is gone from the morning skies, leaving dark conditions.
Finally, Lunsford has advice for the worst-case scenario -- a cloudy Aug. 12: "If anyone is clouded out Monday morning," he says, "rates on Tuesday will also be impressive, much better than those seen the day before maximum."
Perseid meteors are typically white or yellowish with some glowing trains and an occasional very bright meteor called a fireball. Up to 10 shooting stars per hour not associated with the Perseids grace the sky this time of year. These other meteors can approach from any direction in the sky.
Joe Rao is SPACE.com's backyard astronomy columnist. Robert Roy Britt is SPACE.com's senior science writer.
