Every August, just when many people go vacationing in the country where skies are dark, the best-known meteor shower ? the Perseid meteor shower ? makes its appearance.
The "shooting stars" promise to deliver an excellent show this year to anyone with clear and dark skies away from urban and suburban lights.
The best time to watch for meteors will be from the late-night hours of Wednesday, Aug, 11 on through the predawn hours of Aug. 13 ? two full nights and early mornings. Patient skywatchers with good conditions could see up to 60 shooting stars an hour or more. [Top 10 Perseid Meteor Shower Facts]
History of the Perseids
The event is also known as "The Tears of St. Lawrence."
Laurentius, a Christian deacon, is said to have been martyred by the Romans in 258 AD on an iron outdoor stove. It was in the midst of this torture that Laurentius cried out:
"I am already roasted on one side and, if thou wouldst have me well cooked, it is time to turn me on the other."
The Saint's death was commemorated on his feast day, Aug. 10. King Phillip II of Spain built his monastery place the "Escorial," on the plan of the holy gridiron. And the abundance of shooting stars seen annually between approximately Aug. 8 and 14 have come to be known as St. Lawrence's "fiery tears."
We know today that these meteors are actually the dusty remains left behind by the comet Swift-Tuttle. Discovered back in 1862, and most recently observed in 1992, this comet takes approximately 130 years to circle the sun. With each pass, Comet Swift-Tuttle produces a debris trail along its orbit to cause the Perseids.
Every year during mid-August, when the Earth passes close to the orbit of Swift-Tuttle, the material left behind by the comet from its previous visits ram into our atmosphere at approximately 37 miles per second (60 km/second) and creates bright streaks of light in our midsummer night skies.
Excellent prospects this year
According to the best estimates, in 2010 the Earth is predicted to cut through the densest part of the Perseid stream sometime around 8:00 p.m. Eastern Daylight Time on Thursday.
The best window of opportunity to see the shower will be the late-night hours of Wednesday on through the first light of dawn on the morning of Thursday, and then again during the late-night hours of Aug. 12 into the predawn hours of Aug. 13.
The Moon, whose bright light almost totally wrecked last year's shower, will have zero impact this year; unlike last year when it was just a few days past full, this year it will be new on Monday, Aug. 9, meaning that there will be absolutely no interference from it at all.
What to expect
A very good shower will produce about one meteor per minute for a given observer under a dark country sky. Any light pollution or moonlight considerably reduces the count.
The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yields 90 or 100 meteors per hour. Anyone in a city or near bright suburban lights will see far fewer. [Video: Perseid
However, observers with exceptional skies often record even larger numbers. Typically during an overnight watch, the Perseids are capable of producing a number of bright, flaring and fragmenting meteors, which leave fine trains in their wake.
On the night of shower maximum, the Perseid radiant is not far from the famous "Double Star Cluster" of Perseus (hence the name, "Perseid"). Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing. Shower members appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks, and move faster across the sky.
About five to 10 of the meteors seen in any given hour will not fit this geometric pattern, and may be classified as sporadic or as members of some other (minor) shower.
How to watch
Aside from the predicted peak hours, Perseid meteor shower activity always increases sharply in the hours after midnight. We are then looking more nearly face-on into the direction of the Earth's motion as it orbits the sun, so the atmosphere above you scoops up meteors like the windshield of a car catching bugs. From around 2 a.m. until daybreak your local time, the Perseids promise to put on a good display, weather permitting.
Making a meteor count is as simple as lying in a lawn chair or on the ground and marking on a clipboard whenever a "shooting star" is seen. Watching for the Perseids consists of lying back, gazing up into the stars, and waiting. It is customary to watch the point halfway between the radiant (which will be rising in the northeast sky) and the zenith, though it's perfectly all right for your gaze to wander.
Counts should be made on several nights before and after the predicted maximum, so the behavior of the shower away from its peak can be determined. Usually, good numbers of meteors should be seen on the preceding and following nights as well. The shower is generally at one-quarter strength one or two nights before and after maximum.
A few Perseids can be seen as much as two weeks before and a week after the peak. The extreme limits, in fact, are said to extend from July 17 to Aug. 24, though an occasional one may be seen almost anytime during the month of August.
As a bonus every evening now through he heart of the Perseid meteor shower, three bright planets are tightly clustered just after sunset. Venus, Mars and Saturn are easy to spot in the southwestern sky as soon as darkness falls.
- Galleries: Perseids in 2005 and 2006
- Meteor Shower Viewer's Guide
- Top 10 Perseid Facts
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.