Thunderstones of August
August 2008 :
Note: This article may contain outdated information
This article was published in the August 2008 issue of The Skyscraper and likely contains some information that was pertinent only for that month. It is being provided here for historical reference only.
More than 200 years ago scientists believed the appearance of meteors streaking across the sky was an atmospheric phenomenon. Rocks couldn't fall from the sky! However, in 1803 France, a huge fall of about 3,000 "thunder stones" was witnessed by many citizens in broad daylight. Presented with overwhelming evidence, scientists finally accepted that meteorites were of extraterrestrial origin.
Today we know that most meteors are particles stripped off comets and deposited in orbit about the Sun. When the Earth passes through these streams of cometary debris, the meteors plunge into our atmosphere at many miles per second and disintegrate. The displays are called meteor showers. Some solitary and more dense meteors are fragments of asteroids.
Some individual meteors do reach the ground as meteorites. Two houses in Wethersfield, Connecticut, one mile from each other, were struck in 1971 and 1982. A car was heavily damaged by a 27.3 pounder in Peekskill, New York on October 9, 1992. And I found a report about a Georgia woman being struck, but not killed, by an eight pound meteorite in 1954. Occasionally a larger and more fragile piece may fragment and scatter hundreds of meteorites over a wide area, like the 1803 French event.
Though such events are rare, they do occur from time to time. However, don't let this deter you from enjoying the annual Perseid meteor shower peak on the morning of August 12. The likelihood of being struck by a meteorite is astronomical!
Outdoor activities abound during August, and this fact contributes to the Perseids being the most well known of all the meteor showers. And this year observing conditions will be quite good. Unfortunately the shower peaks on a week night/morning, so you'll need to catch a few zzzz's if you can before beginning your observing run.
On peak morning the waxing gibbous Moon (midway between First Quarter and Full) will set around 1:15 a.m. for southern New Englanders. That timing will provide a dark sky observing window of about three hours or so before dawn's early light brightens the sky. If you can, select a location well away from light pollution and get comfortable on a lounge chair or in sleeping bag. Remember the bug spray!
The Perseids appear to radiate from an area of sky, called the radiant point, in the constellation Perseus. Perseus is well up in the northeast sky after midnight. Face this general direction when you first begin your observing session and gradually follow the radiant across the sky. As Perseus rises higher into the sky, the number of meteors will increase as the morning progresses.
With the Moon absent, and assuming a minimum of light pollution, an observer may see between 60 and 90 meteors blazing across the heavens at 134,222 miles per hour. The Perseids are usually green, red or orange in color. And some members of this shower are bright and often produce exploding fireballs. Also, fireballs may be more prevalent as we approach morning twilight. Why? At that time we are hitting the meteor stream head- on! Hopefully you'll see more shooting stars than fireflies.
Mother Nature is not often kind to us around here when it comes to astronomical events. So, if bad weather is forecast for peak morning, try observing the morning before and/or the morning after if the weather cooperates. You'll see about one quarter of the peak night rates, or about 15-25 meteors per hour at best.
Good luck with the best meteor shower of the year. Just one word of caution ... if you suddenly see a bright meteor that appears to be heading in your direction, duck!
Don't forget to visit Seagrave Memorial Observatory on Peeptoad Road in North Scituate this summer on any clear Saturday night. Jupiter will once again be well placed for observing. Check out his four bright moons as they orbit around this giant planet. Also be sure to ask one of our volunteer telescope operators to show you a few of summer's heavenly wonders, like globular cluster M13, the Ring Nebula (M57) and beautiful double star Albireo.
Visit our web site for additional information: www.theskyscrapers.org.
Keep your eyes to the skies.
