Last modified: Monday, July 29, 2002
Perseid meteor shower a summer highlight
Watching the Perseid meteor shower is a summer tradition for many people. This year at the shower's peak the moon will be just three days past new and will set early, leaving the stage darkened for a pleasing show on a warm summer night.
The Perseids will peak on the night of Aug. 11-12 and perhaps on Aug. 12-13 as well. Normally, the best meteor-watching time is between midnight and the start of morning twilight. The best strategy may be to get up very early on Aug. 12 or 13 instead of staying up late the night before. Meteor activity tends to rise during the pre-dawn hours, and the chance of seeing fireballs increases as well.
The Perseid shower's peak rate is typically about 60 meteors per hour under ideal conditions, when the sky is clear and there are no bright sources of light nearby. Try to get away from as many artificial lights as possible to minimize the effect of light pollution, which can obscure as many as half of the visible meteors. A reclining lawn chair will make it easier to watch the sky if you can stay awake.
The early morning hours are when Earth's rotation will bring your viewing site into the path of the oncoming stream of meteors, which makes the greatest number of meteors visible. There will be some meteor activity for a few hours on either side of the peak time, as well as during the nights immediately before and after the peak.
The meteors may appear anywhere in the sky, but they will seem to originate from a point in the constellation Perseus, from which the Perseids get their name. The higher this apparent point of origin is above the northeastern horizon, the more meteors will be visible. Perseus is just north of the W-shaped constellation Cassiopeia in the Milky Way.
Most meteor showers happen when Earth crosses the orbit of a comet. The meteors are caused by tiny particles of dust that were released from the comet's nucleus and left behind in space as the comet got closer to the sun. The Perseids come from Comet Swift-Tuttle. As Earth plows through this stream of particles, each one hits our upper atmosphere at a speed of more than 100 kilometers per second and burns up almost instantly from friction with air molecules. The resulting heat momentarily creates a streak of glowing air that we see as a meteor (sometimes called a "shooting star" or "falling star").
Meteor watchers who would like to contribute to ongoing efforts to study meteor showers can contact the International Meteor Organization at http://www.imo.net for instructions on how to report observations of meteors. More information about the Perseid shower is available at http://skyandtelescope.com/observing/objects/meteors/article_649_1.asp.
Venus will continue to adorn the western sky after sunset during August, gleaming white as a lovely "evening star" while the sky is still light. It will set less than two hours after the sun. Venus will be rather low in the west for viewers in the Northern Hemisphere but almost halfway up the sky for those watching in the Southern Hemisphere. On the evenings of Aug. 30 and 31, Venus will be very close to the bright white star Spica.
As seen from the Northern Hemisphere, Mercury will be barely above the western horizon a half hour after sunset during August, far to the lower right (north) of Venus. Unless you have a telescope and a clear view of the horizon, Mercury will probably be too difficult to find in the bright evening twilight during the short time before it sets. For observers in the Southern Hemisphere, however, Mercury will be well above the horizon and easy to locate as the evening sky darkens.
Saturn will rise about three hours before the sun in early August, but by month's end it will appear within an hour after midnight local time. Saturn's famous rings will be easily visible in a clear dark sky with a tripod-mounted telescope. The best time to view them in August will be just before the start of morning twilight, when the yellow planet will be highest.
Jupiter will rise three hours after Saturn, regaining its usual status as the brightest object in its part of the sky. Brilliant white Jupiter yields only to Venus and the moon in brightness.
Mars will be out of sight behind the sun for the next few months.
The moon will be at third quarter on Aug. 1, new on Aug. 8, at first quarter on Aug. 15, full on Aug. 22 and at third quarter again on Aug. 31.