Don't miss the wonder. &;-)
Posted on 08/12/2002 3:44:34 AM PDT by 2Trievers
Every August, just when many people go vacationing in the country where skies are dark, the best-known meteor shower makes its appearance. As with many celestial phenomena, there's some curious lore surrounding the shooting stars of the annual Perseid meteor shower.
|
|
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 supposedly 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."
It is highly doubtful whether this actually happened or was a product of morbid medieval imagination, but King Phillip II of Spain believed it enough to build his monastery place, the "Escorial," on the plan of the holy gridiron. The saint’s death was commemorated on his feast day, Aug. 10.
The abundance of shooting stars seen annually between approximately Aug. 8 and 14 have come to be known by some as St. Lawrence’s "fiery tears."
Trail of debris
We know today that these meteors are the dross of a comet called Swift-Tuttle.
Discovered in 1862, this comet takes approximately 130 years to circle the Sun. And in much the same way that the Tempel-Tuttle comet leaves a trail of debris along its orbit to produce the spectacular Leonid meteors of November, the Swift-Tuttle comet produces a debris trail along its orbit to generate the Perseids.
Indeed, 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 rams into our atmosphere at approximately 37 miles per second (60 kilometers per second) and creates bright streaks of light in the midsummer night skies.
According to the best estimates, in 2002 the Earth is predicted to cut through the densest part of the Perseid stream sometime between 6 p.m. and 9 p.m. EDT on Monday, Aug. 12. This is during the late afternoon and early evening hours across North America, and while the actual interval of peak activity might be lost to daylight, the predawn hours of both Monday morning, the 12th, and Tuesday morning, the 13th, still holds the promise of seeing a very fine Perseid display.
For Europe, the peak comes near or soon after midnight on Aug. 13. Few Perseids are ever visible from the Southern Hemisphere.
The Perseids are considered active from about July 25 through Aug. 18, and hourly rates usually rise above 10 starting about Aug. 8. Rates fall off much more rapidly after the peak, dropping again to below 10 per hour after about Aug. 14.
The Moon, whose light partially interfered with last year’s Perseids, will not do so this year. It will be a lovely crescent phase in the early evening sky after sunset, even hovering near the brilliant Venus on Sunday, the 11th. The Moon will set around 10:15 p.m. Sunday night and about a half hour later on Monday, the 12th, leaving the sky dark for the early morning hours, which tend to be prime-time for meteor viewing.
What to expect
Based on recent history, a very good Perseid shower will produce about one meteor per minute for a given observer under a dark country sky. Any light pollution, moonlight or hazy skies considerably reduces the count.
The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity can yield 50 or 60 meteors per hour. However, observers with exceptional sky conditions often record even larger numbers. Also, 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. Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing. Meteors appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks, and move faster across the sky because of our view of their trajectory.
About five to 10 additional meteors in any given hour will not fit the geometric pattern of the Perseids and may be classified as sporadic meteors or as members of some other lesser shower.
Perseid activity increases sharply in the hours after midnight, so plan your observing times accordingly. If time is short, you can simply set your alarm for 3 a.m. and watch the last couple hours of the event. We are then looking more nearly face-on into the direction of the Earth’s motion as it orbits the Sun, and the radiant is also higher up, so viewing conditions are optimal.Meteors and myth Finally, comets and meteor showers tend to fuel myths Let's dispel one here:
Many years ago, a phone call came into New York’s Hayden Planetarium. The caller sounded concerned about a radio announcement of an upcoming Perseid display and wanted to know if it would be dangerous to stay outdoors on the night of the peak of the shower (perhaps assuming there was a danger of getting hit). These meteoroids, however, are no bigger than sand grains or pebbles, have the consistency of cigar ash and are consumed many miles above our heads.
The caller was passed along to the Planetarium’s chief astronomer, who commented that there are only two dangers from Perseid watching: getting drenched with dew and falling asleep.
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.
Don't miss the wonder. &;-)
Not going to take a chance on a mosquito giving me West Nile-itis.
Wouldn't be prudent.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.