Jimmy Westlake: A great year for Leonid meteors
November 10, 2009
Less than a year after the end of the American Civil War, two astronomers independently discovered a comet that now bears their names: Ernst Tempel, of France, and Horace Tuttle, of the United States.
Tempel and Tuttle discovered that their comet follows an elongated orbit around the sun, returning to the vicinity of Earth every 33.2 years, and that the geometry of the comet's orbit is such that it intersects Earth's orbit in mid-November every year.
It is the debris shed by Comet Tempel-Tuttle that creates our annual Leonid meteor shower when the Earth encounters the comet's orbit each November. Usually, the Leonid meteor shower generates only a dozen or so swift meteors each hour near its peak, but in the years after the passage of the parent comet near the Earth, spectacular meteor storms have been observed. Take, for example, the Great Leonid Meteor Storm of Nov. 13, 1833, when an estimated 100,000 meteors filled the sky each hour. This is the legendary night the "stars fell on Alabama." A young Abraham Lincoln apparently witnessed this event from New Salem, Ill. Later in life, when asked whether he thought the Union would come to an end as a result of the war, he related the following story:
"When I was a young man in Illinois, I boarded for a time with a deacon of the Presbyterian church. One night I was roused from my sleep by a rap at the door, and I heard the deacon's voice exclaiming 'Arise, Abraham, the day of judgment has come!' I sprang from my bed and rushed to the window and saw the stars falling in great showers! But looking back of them in the heavens, I saw all the grand old constellations with which I was so well-acquainted, fixed and true in their places. Gentlemen, the world did not come to an end then, nor will the Union now." (D. Olson and L. Jasinski, Sky & Telescope, November 1999)
Every 33 years, when Comet Tempel-Tuttle comes around, Earth can experience another Leonid meteor storm. Such a year was 1966. As a budding young astronomer of 13, I fell asleep in my sleeping bag about 1 a.m. and slept through the most intense meteor storm of all time — more than 500,000 meteors per hour. My next chance to see a Leonid storm came Nov. 18, 2001, when I counted "only" 1,200 meteors per hour from Arches National Park in Utah.
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In off years, such as 2009, the Leonids are usually not very active, but if meteor forecasters are correct, 2009 could produce very strong showers of meteors for parts of the world. Folks living in Asia are best placed for the flurry of activity, where meteor rates might be measured in the hundreds per hour. We in North America aren't left completely out in the cold, though, as our rates might shoot up to several dozen meteors per hour.
The shower's radiant, in the head of Leo the Lion near the bright star Regulus, doesn't rise into our sky until nearly midnight, so, the best time to watch for Leonid meteors will be between midnight and dawn on the mornings of Nov. 17 and 18. The moon is near its new phase and will not interfere at all, making this an outstanding year for watching the Leonid meteor shower.
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 & Today. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's Web site at http://www.jwestlake.com.