Jimmy Westlake: Perseids compete with Fruit Moon
August 10, 2011
Steamboat Springs — Two of my favorite things happen in early August every year: The serviceberries ripen, and the Perseid meteors shoot across the sky. It seems I spend my waking hours scanning the high branches for the sweet Rocky Mountain berries and what should be my sleeping hours scanning the skies for shooting stars. There's time for sleep this winter.
The annual Perseid meteor shower is under way and is expected to peak before dawn on Saturday. 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 60 or more shooting stars per hour at its peak, under good conditions.
The Perseid meteor shower has been observed in early August every year since at least 258 A.D., when the Romans martyred a Christian deacon named Laurentius on a hot gridiron. That night, as Laurentius' 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 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 easily could 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 point toward the constellation of Perseus in the northeastern sky. The night of peak activity is Friday and Saturday, but some Perseid meteors can be seen for about a week on either side of the peak. You always will 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 streaming.
August's bright full moon, called the Fruit Moon, will greatly reduce the number of meteors visible in 2011. Only the brightest Perseids will be able to compete with the moonlight on the morning of the peak.
Your best chance for seeing some Perseids in a dark sky will be a few mornings before the predicted peak, after the fat gibbous moon has set.
The good news is that in 2012, the waning crescent moon will pose no threat to the peak of our favorite summertime meteor shower.
Enjoy the serviceberries and the meteors!
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 Today newspaper. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's astrophotography website at http://www.jwestlake.com.
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