By Jimmy Westlake, professor of physical science, Colorado Mountain College in Steamboat
The annual Perseid meteor shower is now underway and is expected to peak on Thursday August 12. While some meteor showers can disappoint because of slower than expected activity, the Perseid meteor shower is the “old faithful” of meteor showers because it dependably produces 50-60 meteors per hour at its peak.
The Perseid meteor shower has been observed in mid-August every year since at least 258 AD, when the Romans martyred a Christian deacon named Laurentius on a hot gridiron. That night, as Laurnetius’ family and friends carried away his body, they noticed a number of bright streaks falling through the sky and they marveled at the miracle, believing that the streaks were the fiery tears of Laurentius falling from heaven. Centuries later, people the world over continue to marvel at the sight of “St. Lawrence’s tears” every August.
In the year 1862, American astronomers Lewis Swift and Horace Tuttle discovered a comet that now bears their names. Four years later, Italian astronomer Giovanni Schiaparelli noticed that the particles that cause the Perseid meteors seemed to follow the same orbit as the orbit of Comet Swift-Tuttle. That was the first indication that comets could be the source of our annual meteor showers.
We now know that the Perseid meteors are produced when tiny bits of space dust, shed by Comet Swift-Tuttle, enter the Earth’s atmosphere at 130,000 mph and burn up as meteors about 60 miles high. These dust particles are so tiny that you could easily hold 1000 of them in the palm of your hand.
Perseid meteors can be seen in all parts of the sky, but their trails will all point back toward the constellation of Perseus. The night of peak activity is August 12-13, but some Perseid meteors can be seen for about a week on either side of that date. You will always see the most meteors between midnight and dawn because that’s when the spinning Earth has you facing the direction from which the meteors are coming. This year, the crescent moon will set early in the evening and leave the midnight sky dark for meteor watching.
If you are interested in trying to photograph Perseid meteors, all you need is a camera capable of taking time exposures of one minute or longer, mounted firmly on a tripod. Use film or a digital ISO setting of at least 400 speed for best results. Set your camera focus on infinity, aim it at a point about halfway up in the sky, open the shutter, and wait. If you are very lucky, one or more meteors might streak through your picture in a one-minute exposure.
So, whether you are out camping at the lake or just viewing from your own back yard, grab a comfy recliner and sleeping bag, some insect repellant, and a thermos of your favorite hot beverage, and watch the sky for St. Lawrence’s tears. You never know when the next big one will flash into view. ***
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. His “Celestial News” column appears weekly in the Steamboat Pilot newspaper. His “Cosmic Moment” radio spots can be heard on local radio station KFMU. Also, check out Jimmy’s website at www.jwestlake.com.