The Leonid Meteor Storm 1999

On the 12th November 1999 around 70 people, including approximately 50 members of the BAA Meteor Section, flew out of Gatwick Airport bound for Sharm el Sheikh, Egypt, for the Explorer’s Tours Sinai Star Party- a week of Astronomy talks, observing sessions and sight-seeing around the Red Sea coast. The Star Party’s focal point was the observation of the Leonid meteor shower in anticipation of the prediction by Asher and McNaught that a storm would occur around 02:00 UT (04:00h local time) on the 18th November.

A site in the Sinai Desert mountains, about an hour’s drive from Sharm el Sheikh, was chosen for observation for a number of reasons:

mild climate (night time temperatures in the low 20’s ºC) high probability of clear skies (on average 350 clear nights/year), an acceptably dark sky for viewing (reasonably distant from sources of light pollution), latitude and longitude were such that the Leonid radiant was almost overhead at the time of the predicted maximum, giving an all-sky view of the meteor shower.

On the night of the 16th/17th we arrived at the site around midnight and waited (and waited) just in case something unexpected would happen. (Nothing did!). Conditions for viewing were a revelation- clear dark skies and warm air, a world away from the norm in Scotland! Leonid rates were moderate (ZHR around 40/hr) being out-numbered by sporadics and Taurids (also active during November). We packed up around 05:15h when the dawn twilight began to interfere and headed back to the hotel by bus. As the sun rose from the unobscured sea horizon we were treated to the unexpected sight of a large sunspot group clearly visible to the unaided eye.

Expectations were high on the night of the 17th/18th as we departed for the viewing site at 22:00h. Conditions were again ideal. We set up our equipment in leisurely fashion and waited until moonset at around 00:30h. Very few meteors were noted during the time that the moon was in the sky, a testament to the impact of the moon’s light upon the sky background and limiting magnitude. After moonset there was an enhancement in meteor count, with rates of around 180/hr rising perceptibly as time passed by.

By 03:15h, an observer viewing any part of the sky was seeing an impressive 8 Leonids/min, but the storm was yet to come! From around 03:45h rates rose noticeably from one minute to the next. Between 04:00h and 04:05h the view was totally awesome- meteors were raining down from the heavens at more than 50/min, no matter what part of the sky was being observed. During the peak, at times four, five, six, (or more!) meteors appeared simultaneously, the desert silence being broken by the cries of wonderment from the enthralled spectators, and by the good-natured complaints emanating from the BAA meteor counters, who were overwhelmed by the sheer volume of meteors visible.

Just forty-five minutes later, the storm had subsided to a mere shower with rates returning to around 8/min and we were left to ponder the spectacle just witnessed. Even so, the show was not over yet, as several times in the next hour the landscape was momentarily illuminated by a flash of light as a bright Leonid sped to oblivion through the Earth’s atmosphere. Even as we were packing up in the pre-dawn twilight with only the brightest stars visible, several times our attention was drawn skywards by flashes of light as Leonids continued to fall.

Leaving the desert behind on our way back to the hotel we were all well-satisfied by the spectacle we had been privileged to see and by the knowledge that we had definitely been in the right place at the right time.

The vast majority of the Leonids observed were only of moderate brightness (magnitude ~2-4), fast moving and most left a characteristic green train lasting a second or so. During the night there were only a few Leonids of magnitude -2 to -3, but each lit up the landscape and drew excited reaction from the appreciative on-lookers. The display was therefore very different to that of 1998, which featured a large number of fireballs, some rivalling the full moon in brightness.

Asher and McNaught’s predictions for 1999 were remarkably close to reality, both in the timing of the maximum and in peak activity. Their model predicts that high activity will remain over the next few years. Unfortunately, the moon will interfere in 2000, but prospects for a storm in 2001 are good, where observers on the west coast of North America and the Pacific area will be best-placed for the predicted storm.

Anyone for an encore?