http://science.nasa.gov/headlines/y2002/19jul_perseids.htm <br /> <br />Summer Meteor Shower<br />NASA Science News<br /><br />The Perseid meteor shower peaks this year on Aug. 12th and 13th. The warmth<br />of northern summer makes it one of the year's most inviting sky shows.<br /><br />July 19, 2002: Perseid meteors are fast, bright and colorful. The annual<br />Perseid shower is one of the year's best--really spectacular. But that's not<br />why I love watching them. The real reason is ... the Perseids are<br />comfortable.<br /><br />Remember the Leonid meteor storm last November? Great meteors. Frigid<br />weather. Most northern meteor showers are like that.<br /><br />But not the Perseids. They come in August when the cool night air is<br />refreshing not bone chilling. I can shuffle outside at 3 a.m. in my pajamas<br />and still enjoy the show.<br /><br />This year the shower peaks on August 12th and 13th. Experts say it should be<br />remarkably good. The Perseids have been strong in recent years--a promising<br />sign for 2002. And the moon sets early in mid-August; lunar interference<br />will not be a problem. Sky watchers can expect to see dozens to hundreds of<br />meteors per hour.<br /><br />Perseid meteors come from comet Swift-Tuttle. Every 130 years, the comet<br />swoops in from deep space (beyond Pluto) and plunges through the plane of<br />the solar system not far from Earth's orbit. Astronomers once worried that<br />Swift-Tuttle might hit our planet, but recent data and calculations show<br />otherwise. There's no danger of a collision for at least a millenium and<br />probably much longer.<br /><br />Even so, little pieces of Swift-Tuttle do hit Earth. The comet's orbit is<br />littered with bits of dusty debris. They bubble away from the comet's icy<br />nucleus (propelled by evaporating ice) when Swift-Tuttle nears the Sun.<br />These grains form a cloud that we plow through once a year.<br /><br />We're entering the outskirts of that cloud now (late July). Every hour, one<br />or two meteors are streaking across the sky. It's the slow beginning of the<br />Perseids.<br /><br />Perseid dust particles are tiny, most no bigger than grains of sand. Yet<br />they travel very fast--about 132,000 mph (59 km/s). Even a tiny dust speck<br />can become a brilliant meteor when it hits the atmosphere at that speed.<br />There's no danger to sky watchers, though. The fragile grains disintegrate<br />long before they reach the ground.<br /><br />Because of the way the comet's orbit is tilted, dust from Swift-Tuttle falls<br />on Earth's northern hemisphere. Viewed from Earth's surface, the meteors<br />appear to flow from the constellation Perseus (hence the name Perseids).<br />Perseus is easy to spot from Europe and North America, but it barely peeps<br />above the horizon of, e.g., Australia and New Zealand. Southern hemisphere<br />sky watchers will see very few Perseids.<br /><br />The following is true no matter where you live: The best time to look for<br />meteors is when Perseus is highest in the sky--between 2 a.m. and dawn. On<br />August 12th, set your alarm for 2 o'clock in the morning. Go outside; lie<br />down on a sleeping bag or a reclining lawn chair with your toes pointed<br />northeast; and gaze upward. Soon you'll see shooting stars racing along the<br />Milky Way.<br /><br />Repeat the procedure on August 13th. The shower's peak is long-lasting, and<br />you're likely to count plenty of meteors on both days. (The shower is<br />expected to crest on August 12th during a 12 hour period centered on 2200<br />Universal Time. Dawn on August 13th would therefore be best for Europeans.<br />Dawn on either day could be good for North Americans.)<br /><br />Can't wake up at 2 a.m.? Try looking for Perseids instead around 9 or 10<br />p.m. when Perseus is hanging low. (Note: it's always hanging low in the<br />southern hemisphere.) You won't see many meteors then, but the ones you do<br />see could be memorable. Shooting stars that emerge from the horizon and<br />streak horizontally through the atmosphere are called Earthgrazers. They are<br />remarkably slow, colorful and bright.<br /><br />Earthgrazers are a good target for city dwellers. Urban lights wipe out the<br />rush of faint meteors that streak across darker skies. From a big city you<br />can see only the brighter ones.<br /><br />Perhaps August would be a good time for a trip to the country. There you can<br />see the faint Milky Way and hundreds of Perseids ... and maybe no one will<br />notice if you shuffle out in your pajamas to watch the stars.