November 1, 2002
Alan MacRobert, Senior Editor
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After putting on spectacular performances for the last four years running, the Leonid meteor shower will once again sweep over Earth during the early-morning hours of Tuesday, November 19th, Sky & Telescope magazine reports. If the weather is clear, we could be in for a grand celestial show.
Every year since 1998 the world has witnessed an impressive meteor shower around this date, when Earth passes through a narrow stream of rubble in space left by Comet Tempel-Tuttle. Meteor showers have long been hard to predict accurately, but astronomers' experience with the Leonids in the last several years has finally given them a good handle on the subject. In 2001 meteor astronomers got it just right. Countless thousands of skywatchers alerted by Sky & Telescope and other news media went out before dawn at the predicted date and time and witnessed the richest meteor display over North America in 35 years.
This year meteor forecasters predict that we will again get a strong shower — and maybe even a "meteor storm" — at certain times on the morning of November 19th. They also say this will probably be the last strong Leonid shower that Earth will encounter for a century.
Unfortunately, bright moonlight this year will fill the sky and compromise the view. Faint meteors will be mostly hidden in the moonlight, though bright ones should show through just fine.
According to the November 2002 issue of Sky & Telescope, this year's shower is likely to come in two waves, each lasting a couple of hours, that will peak around 4:00 and 10:40 Universal Time (UT, also called Greenwich mean time, GMT) on the 19th. What that means to you depends on where on the globe you are located.
The first peak is well timed for skywatchers in Europe, North and West Africa, and northeasternmost North America. The second peak favors all of North America, but especially the central and western parts of the continent.
When is the best time to watch? That depends on your time zone. Here's a rundown:
Eastern time zone: If you're in the U.S. Northeast or the Canadian Maritimes, you can start watching the sky as early as 11:30 p.m. EST on Monday night the 18th. The first peak will already be passing, but not until about this time will the shower's apparent point of origin (its "radiant" in the constellation Leo) rise above your horizon, allowing any meteors at all to reach your part of the world. Watch for a few very long, spectacular streamers passing overhead — meteors skimming the top of the atmosphere above you almost horizontally. They'll be flying roughly east to west. Keep watching until at least 1 a.m.
The second peak should pick up steam before and during dawn Tuesday morning. These meteors will be shorter and perhaps more numerous. Start looking two hours or more before sunrise (in other words, approximately 4:30 a.m. EST; look up your local sunrise time in the newspaper or use the almanac on Sky & Telescope's Web site and work backward from there). The nominal peak should come around 5:40 a.m. EST. Depending on where you live, the meteors may keep increasing in numbers right up until they fade from sight in the growing light of day.
Central time zone: On Tuesday morning, watch from about 3:30 a.m. CST onward. The shower is predicted to peak around 4:40 a.m. and will probably be tapering off by the beginning of dawn. (The first peak, described for the eastern time zone, is out of sight from here and points west.)
Mountain time zone: On Tuesday morning, watch from about 2:30 a.m. onward. The meteor shower is likely to peak around 3:40 a.m. MST.
Pacific time zone: On Tuesday morning, watch from about 1:30 a.m. onward. The shower is likely to peak around 2:40 a.m. PST.
What direction should you look? "Up!" says Sky & Telescope senior editor Alan MacRobert. "The meteors will appear all over the sky, so just watch whatever part of your sky is darkest. Keep the Moon out of your view so it doesn't dazzle your eyes."
Here are some other meteor-watching tips. Dress very warmly, because it will be colder than you think (due to radiational cooling under a clear sky). Find a spot with a good sky view and no bright lights nearby. Lie on the ground or in a reclining lawn chair, preferably in a warm sleeping bag, so you can keep a comfortable watch on the stars for a long time without getting a crick in your neck. Just relax and gaze into the stars.
You may notice that all of the Leonids have something in common. Their paths, if traced backward far enough across the sky, would appear to diverge from the same spot in the eastern sky, in the Sickle pattern of the constellation Leo, the Lion.
What is a meteor? What you're seeing is a white-hot streak of superheated air caused by a sand- or pebble-size grain plunging into the Earth's upper atmosphere at high speed. The Leonids arrive at a blistering 44 miles per second (71 kilometers per second).
Last year Leonids peppered the skies over North America at rates of up to 1,000 per hour visible by any given observer. Three years ago skywatchers in Europe and the Middle East saw 3,000 per hour, nearly one every second. In 1966 lucky observers in the southwestern United States gaped in awe for 20 minutes as Leonids fell at the rate of 40 per second! This year the visible rates may range from one every few seconds to a couple of meteors a minute.
All this comes with a caveat. Meteor predicting is still an inexact science. The only way to know for sure what will happen on the morning of November 19th is to go out and watch.
More about the Leonid shower appears in the November 2002 issue of Sky & Telescope, the world's leading astronomy magazine, and on its Web site at http://SkyandTelescope.com/observing/objects/meteors/article_719_1.asp.
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