International Meteor Organization - Science note on the Leonids 2000

What happened up to now?

In 1998, no veritable Leonid storm was seen, but a - then - unexpected and very impressive fireball shower developed during the first morning hours of 17 November. Subsequent calculations convincingly demonstrated that large dust particles released by the Comet 6 to 7 centuries ago were responsible for this phenomenon. Normally, dust particle filaments that old have completely faded away and are incapable of producing significantly enhanced activity, but, because of the particular geometry in this case, the gravitational pull of the giant planet Jupiter managed to keep the larger dust particles of the filament together.

The unexpected events of 1998 encouraged astronomers to develop more reliable models for predicting meteor shower activity. Especially the model of astronomers David Asher and Robert McNaught attracted a lot of attention. Their prediction for a meteor storm in 1999 proved to be correct, both with respect to the time of maximum and the order of magnitude of meteor activity.

The 1999 Leonids peaked around 2:02 a.m. Greenwich Mean Time. Several tens of meteors per minute were visible at that time, corresponding to a frequency of 3700 meteors per hour as obtained from averaging reports from hundreds of observers at various locations. Many favourable observing locations suffered from clouds, unfortunately. The most successful observations were carried out in the Middle East, the French Provence, Southern Spain, and the Canary Islands.

Two striking features of the 1999 Leonids deserve mentioning. First, there were a lot of local variations in the activity profile. In order to understand these variations, it is essential to have observations from as many locations as possible and analyse them collectively and comparatively. Precisely this is the most important aim of the International Meteor Organization.

Second, the brightness distribution was very atypical. The shower was poor in both very bright and very faint meteors. Normally, it is either one or the other. Finally, it must be noted that observers in Hawaii and the Far East witnessed a secondary peak around 16h Greenwich Mean Time on 18 November, yielding 180 meteors per hour.

	When do we see Leonid meteors?
	What may be expected this year?

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Last Update: 08 Sep 2005