The prospects for a possible meteor storm generated by the Leonid meteor shower in 1999 are examined. Observed Leonid shower maxima from the seven most recent storms are investigated. The average values of these seven storms for Delta T (Earth at node) and C-E (the minimum distance between the orbit of Comet 55P/Tempel-Tuttle and the Earth) compare favorably with the upcoming 1999 values, suggesting that the odds for a storm occurring are now probably at their best for the current Leonid apparition. The production of meteor trails by the parent comet is discussed. It appears that the meteor storms of 1833 and 1966 were caused by meteor trails that were produced respectively in 1800 and 1899. Perturbation of the 1800 trail by Saturn and Jupiter apparently was responsible for the lack of any significant Leonid activity in 1899, while the meteor trail created in 1899 was not yet wide enough to interact with the Earth in 1933 (though a storm did occur on the second revolution of these particles in 1966). An attempt is made to integrate the 1899 meteoroids forward in time from 1966 in order to determine if it is capable of producing another storm in 1999. Through several orbit simulations, it is determined that the 1800 trail was more severely perturbed than was originally believed in 1899 and that the 1966 meteoroids likely underwent a perturbation by Uranus in May 1982, pushing them closer to the Earth's orbit for 1999. The distance between the meteoroid's orbit and that of Earth's (M-E) is found to be 0.0026 AU, which compares favorably with C-E values for the 1833 and 1966 storms. Two methods (extrapolation from past solar longitude values and a comparison between C-E distances and nodal crossing/max. activity times) are used to determine a peak time for the 1999 Leonids. It is found that the peak (on November 18) is most likely to come anywhere from 21 to 150 minutes after the time of Earth's 1h47m UT crossing of the comet node, placing Europe and North Africa in prime viewing position. The latter time might even allow the peak to be glimpsed from eastern North America. Although, in conclusion, is it noted tat circumstances appear favorable for a strong and impressive Leonid showing in 1999, caution is still advised because of the inherent risks involved in meteor shower predictions.
WGN, Journal of the International Meteor Organization
- Pub Date:
- June 1999