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Background on the Leonid Meteor Storm of 2001

by Fred Espenak

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1833 Leonid Storm
(ClIck to Enlarge)
1833 Leonid Storm

Several times each year, the Earth crosses the orbits of old comets, which are no longer visible in our skies. These orbits around the Sun contain dust and sand grain size debris expelled from comets on previous visits to the inner Solar System. As Earth plows through these leftover particles, they enter our atmosphere with such high velocities that air friction causes them to burn up in a brief flash we call a meteor.

Annual meteor showers are known by the constellations from which the meteors appear to radiate. The Leonid shower is one of the most dependable ones and is seen each year around November 18. These "shooting stars" from the constellation Leo are produced from dust left by Comet Tempel-Tuttle. At the peak of each Leonid shower, you can usually see one meteor each minute, but back in 1833 the sky was afire with many meteors each second! Eyewitnesses said the meteors appeared too quickly to count! Such a display of celestial fireworks had never been reliably documented before. Thirty-three years later, another incredible Leonid meteor storm was seen in 1866. It was quickly realized that the 33-year period of the meteor storms coincided with the 33-year period of Comet Tempel-Tuttle. The next storm was eagerly awaited in 1899 but it failed to materialize.

Astronomers looked for meteor storms in 1932-33 but were again disappointed. The 1966 Leonid storm caught the world by surprise since everyone had forgotten about the possibility of such a storm. Ever since then, meteor scientists have been awaiting the Leonid showers of 1999, 2000 and 2001 to see if another great storm would occur.

Early understanding of the meteor storms failed to take into account the exact geometry of Earth's orbit with previous passages of Comet Tempel-Tuttle. The gravitational pull of the planets slowly changes the orbit of Tempel-Tuttle and its dust trails. Recent advances in meteor stream modeling by astronomers McNaught (Australian National University) and Asher (Armagh Observatory) have successfully predicted a Leonid storm for the very first time. The peak of the 1999 Leonid storm was predicted to within five minutes and produced spectacular meteor rates of 3500 per hour (one per second) from Europe and the Middle East (Sky & Telescope, June 2000, page 30-40). Although no Leonid storm was seen in 2000, McNaught and Asher correctly predicted a better than normal meteor shower.

The excitement is now mounting for the 2001 Leonid storm. McNaught and Asher have staked their reputations that this will be the Great Storm that everyone has been waiting for. They predict two peaks about fifty minutes apart when the meteor rates may reach 15,000 per hour (four meteors per second)! The sky will once again be afire with meteors!

Although the USA will miss the event, Australia is in a prime position to view the Great Meteor Storm of the Century! Additional details of the McNaught-Asher predictions may be found at http://www.arm.ac.uk/leonid/dustexpl.html.



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For Fred Espenak's descriptive account and photographs, see:

Report on the 2001 Leonid Meteor Storm

2001 Leonid Storm Photo Gallery

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Additional Links for Leonid Meteors

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All photographs are copyright by Fred Espenak.
Please contact him (at MrEclipse) for all uses of these images
in print, web, video, CD and all other media.

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Last revised: 2003 Dec 27