The recurring Leonid Meteor showers have been fascinating humans for many years. Read about the early thinking and observations of this November occurrence.
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- 902 AD - the first annecdotal account In 868 AD, a yet undiscovered comet crossed the Earth's orbit on the inside for the first time. The comet's orbit had been gradually changing in previous centuries. Shortly thereafter, in 902 AD, Chinese astronomers reported seeing the first Leonidstorm. Numerous accounts would follow in the next centuries: "Stars fell like rain" .
- 1799 - Meteors puzzle scientistIn the Americas observers are startled by many meteors. The reknowed German scientist Humboldt and companion Bonpland, who are in Cumana (Venezuela) at the time, record the event and make it widely known in the scientific community. Rumour has it that in 1766 a similar meteor storm was seenover Cumana.
"Tausende von Feuerkugeln und Sternschnuppen fielen hintereinander, vierStunden lang. (...) Nach Bonplands Aussage war gleich zu Anfang der Erscheinungkein Stuck am Himmel so grosz als drei Mond Durchmesser das nicht jeden Augenblickvon Feuerkugeln und Sternschnuppen gewimmelt hatte. Von 4h an horte die Erscheinungallmahlich auf; ..." - Humboldt
- 1833 - The radiant establishedIn 1833, observers are somewhat familiar with Leonid storms. The storm that year is very intense and the eventleads to the first formulation of a theory on the origin of meteors.
"On the night of November 12-13, 1833, a tempest of falling stars broke over the Earth... The sky was scored in every direction with shining tracks and illuminated with majestic fireballs. At Boston, the frequency of meteors was estimated to be about half that of flakes of snow in an average snowstorm. Their numbers... were quite beyond counting; but as it waned, a reckoning was attempted, from which it was computed, on the basis of that much-diminished rate, that 240,000 must have been visible during the nine hours they continued to fall." - Agnes Clerke's, Victorian Astronomy Writer - 1866 -Ernst Tempel and Horace Tuttle independently discover a dim comet. After observing the comet for several weeks, anorbit was calculated. It was found that the orbit was of short period, 33.17 year. In November that year,a Leonid storm was anticipated. The sheer number of meteors startledobservers in Europe, who scrambled to count the numerous meteors and determine the radiant position.An orbit was calculated for the meteoroids assuming a period of 33 years, and the similarity with the comet orbit was discovered.
- 1899 - The disappointmentIt was now well established that the comet and the meteors returned to Earth every 33 years. Thereturn of 1899 was eagerly awaited. That year, many meteors crossed the sky. Strong activity continued until 1902, with rates increasing to storm conditionsin 1901. The sharp main peak of the Leonids was not observed. The comet also did not show itself again.
- 1933 - Bad weather?In 1932 rates went up again, but a big storm was not observed. At the time, it was thoughtthat the shower was lost because of a close encounter with Uranus prior to the 1899 return. Or, perhaps, the storm wassimply missed by the more scientifically oriented observers because of bad weather. Such is not uncommonin the northern hemisphere in the middle of November.
- 1965 - Comet P/Tempel-Tuttle RediscoveredLost for nearly a century, the comet P/Tempel-Tuttle was rediscovered in 1965. Calculations would later reveal that this comet passed closer to the Earth's orbit (0.0032 a.u.) than on any occasion since 1833. Some predicted the return of a storm over Europe.Instead, a tremendous storm of tens of thousands of Leonids fell for a short interval timed by skywatchers in the centraland western United States on November 17th, 1966. This display probably rivaled the historic showers of 1799 and 1833.Within just two hours, observed rates increased from about 40 per hour to flurries of as much as 40 per second!
"We saw a rain of meteors turn into a hail of meteors too numerous to count," - Charles Capen in the San Gabriel Mountains of Southern California
"The meteors were so intense that we were guessing how many could be seen in a one-second sweep of the observers head... A rate of about 150,000 per hour was seen for about 20 minutes." - Dennis Milon, Kitt Peak in Southern Arizona - 1994 - The first Leonid outburst of the new returnThe first increase of Leonid rates announcing the return of the comet was reported in 1994. Astronomer Peter Jenniskens was among the first to notice the high Leonid rates onNovember 18 that year, when the shower was as strong as the Perseids in August. The outburstlasted a little over a day and was rich in bright meteors.
"The night before, we had organised an observing effort for this one, but were all clouded out. Guess my surprise, when I arrived home late thenext night and saw one bright Leonid after another. I sat down on mylawnchair and enjoyed the view in bright Moon- and city-light for the next hour and a half." - Peter Jenniskens
Observations of the Leonids in 1995 and 1996 confirmed the enhanced rates. The parent comet 55P/Tempel-Tuttlewas finally recovered on March 10, 1997, following an accurate prediction of its orbit,and passed perihelion on February 28, 1998.
- 1998 - the Leonid "Filament" first observed in 1994 soared during thenight of November 16/17, 1998 , when observers all over the world were greeted by numerous fireballs and long lasting persistent trains. The peak of this component was overEurope. Researchers onboard Leonid MAC observe a second peak in eastern Asia that isnow thought to be a far encounter with either the distorted 1899 dust trail or the 1932and 1965 dust trails. Only now we know that those trails were not close to Earth's orbitthat year.
- 1999 - The first close encounter with one of the narrow dusttrails of comet 55P/Tempel-Tuttle in this return occurred in 1999, after new shower models hadcorrectly predicted the timing of the meteor storm when Earth would pass dust ejected in 1899. Leonid MAC researchers have a prime view high above clouds just west of Greece,and return with spectacular footage of the storm.
For more information:
- Ancient and medieval observations (G. Kronk)
- Leonids from 1833 until present (G. Kronk)
- Biography of Wilhelm Tempel by J.L.E. Dreyer
