BY JOHN JOHNSTON
The Cincinnati Enquirer
Every so often, something occurs on a grand cosmic scale, a reminder that we're all passengers on a planet called Earth.
A meteor shower, for instance.
The Leonid meteor shower happens every year around Nov. 17, usually without much fanfare. But this year or next could produce more meteors than usual - making it a meteor storm - and that has astronomy buffs like Mary Ann Kronoveter excited.
If the weather cooperates late Tuesday night and early Wednesday morning, the dental hygienist from Anderson Township plans to be outside, bundled up, watching "shooting stars" streak across the sky.
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WEB SITES
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Look for more information on the World Wide Web:
The Sky & Telescope site includes basic information on meteors and history of the Leonids.
http://www.skypub.com/
NASA's Meteor Outburst Mission Homepage includes a photo gallery, historical information, accounts of the 1966 Leonid storm and links to other sites.
http://www-space.arc.nasa.gov/~leonid/index.html
The American Meteor Society site includes a good overview of the Leonids and a list of links.
http://www.serve.com/meteors
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"It's a personal contact with the universe," she says. "It's like reaching out and touching God. It's thrilling."
She could be disappointed, though. Eastern Asia appears to have the best chance this year of seeing a dazzling meteor storm. Still, a nice show is possible in the Tristate in the predawn hours Tuesday and Wednesday. And there's a slim chance local stargazers could witness an intense meteor storm.
This primer - culled from Sky & Telescope magazine, encyclopedias and astronomy Web sites - explains what's out there.
Burning space debris
On most clear, moonless nights a few meteors are visible as brief, harmless streaks of light in the sky. Each white-hot streak is the result of a piece of space debris - a meteoroid - burning up as it enters Earth's atmosphere 50 to 75 miles above ground. Most meteoroids are the size of a sand grain or a pebble. Objects that reach Earth before burning up are called meteorites.
Comets are the source of many meteoroids. As a comet travels through the solar system on a path around the sun, it leaves a trail of dust and other particles. The debris continues to follow the comet's orbit, even after the comet is long gone.
If that trail intersects with Earth's orbit, we see a meteor shower whenever Earth passes through it. Thus, such showers happen regularly.
The Leonids cometh
Earth passes through the Leonid meteor stream each year about Nov. 17. The Leonids are so named because the meteors appear to come from the constellation Leo.
Debris in this stream is from Comet Tempel-Tuttle, which orbits the sun every 33ì years.
Most years, Earth passes through a part of the stream with few meteoroids, which results in an unimpressive shower. But when Earth hits the stream shortly before or after the comet has passed by, the concentration of meteoroids is greater. The comet passed through the inner part of the solar system early this year, so some experts believe a major Leonid storm is due.
The last spectacular storm was 1966 (when some observers in the western United States reported seeing more than 2,000 meteors a minute). Given Comet Tempel-Tuttle's 33-year cycle around the sun, 1999 - not 1998 - might prove to be the big storm, some experts say. The year 2000 also is in the running.
History shows that even when all signs point to a meteor storm, sometimes nothing happens.
"Predictions of meteor storms are notoriously unreliable," David Meisel, executive director of the American Meteor Society, says in November's Sky & Telescope. "No one really knows how to do it properly."
What to expect to see
There's a chance, though extremely slim, that Tristate skies could light up with thousands of meteors in the predawn hours Tuesday or Wednesday. Then again, you might stay up all night and know exactly how Linus felt while awaiting the Great Pumpkin.
For major meteor showers, seeing one meteor every few minutes is typical.
Tuesday and Wednesday, sky watchers with clear weather and a dark sky can expect to see "perhaps a meteor per minute," says Alan MacRobert, associate editor of Sky & Telescope.
Eastern Asia appears to have the best chance of seeing an intense storm this year, because it likely will face the oncoming storm and be in darkness at the critical time. Next year, Europe and Africa probably will be in the best position.
How to watch
The glow from city lights interferes with your ability to see meteors, so it's best to observe in the country. Ms. Kronoveter, a member of the Cincinnati Astronomical Society for three years, plans to observe from the club's dark-sky site in rural Adams County; it's open to members only.
If you can't get out of the city, try to find a place with an open view of the sky, away from street and porch lights. You won't need binoculars or a telescope, just your eyes. Allow them about 15 minutes to adjust to darkness.
The moon is new, so it won't hinder the view.
Bring a reclining lawn chair, lie back, and watch the darkest part of the sky at least 50 degrees up from the horizon. Don't forget to dress warmly.
The best time to watch the Leonids is from 1 a.m. or 2 a.m. until dawn on Tuesday and Wednesday. If you have a choice between staying up late or getting up early, do the latter. The hour or two before dawn should be best.
Satellite survival
The tiny comet fragments that produce the meteor shower pose no danger to people on Earth, but the same can't be said for sensitive satellites in orbit.
The Leonids travel about 43 miles per second - or 155,000 miles per hour. At that speed, a meteoroid that hits a satellite might vaporize into plasma, causing an electric charge that could damage a satellite's electronic equipment.
A dead satellite can affect millions of people who depend on it for information and communication services. Earlier this year, uncontrolled spinning by a satellite shut down most pagers for a day; that problem was because of an internal failure, however, not a meteoroid hit.
Satellite operators are taking various measures to protect their spacecraft from the Leonids, such as re-orienting their machines away from the meteoroids and shutting down non-critical systems. The Hubble Space Telescope will be turned to minimize its exposure.
Harsh Lake viewing
If skies are clear, a Leonid meteor watch and stargazing event will be 7 to 8:30 p.m. Wednesday at the U.S. Army Corps of Engineers visitor center at William H. Harsha Lake in Clermont County. Although the peak of meteor activity will have passed, telescopes will be on hand so visitors can view other celestial objects. Information: 797-6081.
