The Perseid meteor shower, an annual celestial event that's a favorite of skywatchers in the Northern Hemisphere, peaks at 1:00 a.m. EDT on August 13, 2003. But light from the Moon, one day past full, will wash out many of the shower's faint meteors. Subsequent mornings are equally unfavorable. Observers are better off looking for Perseids before maximum, during the brief intervals of dark sky that occur between moonset and the start of morning twilight. For North American observers, this window lasts about a half hour on the morning of August 10th, 1½ hours on the 9th, and 2½ hours on the 8th.
In a dark sky, observers can see 60 or more Perseids per hour. In 2003, skywatchers will see far fewer thanks to "light pollution" from the Moon lighting up the night sky. 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. Perseids can appear anywhere and everywhere in the sky, so the best direction to watch is wherever your sky is darkest. Sit with your back to the Moon, or use a tall tree to block as much lunar light as possible.
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.
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.
Observers can use our interactive
to see the appearance of the sky at 2:00 a.m. during the peak morning of the Perseids. The chart is set at 40° north latitude for central North America. On the chart, the meteor shower name and symbol is visible in both windows. Click on the "change" button to alter either the date and time or viewing location displayed by the chart.
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