Orwell Astronomical Society (Ipswich)
Leonid Meteor Shower, 16-18 November 1998
Explanation and overview of the Leonid meteor shower.
Most predictions of Leonid activity in 1998 placed the maximum within a few hours of 17:00 UT on Tuesday 17 November. However, the peak in fact occurred much earlier than this at about 06:00 UT on the same day; it was spectacular with many very bright meteors and fireballs, with several observers reporting noise from some meteors. Subsequent analysis of observations indicated that the Earth passed through a stream of debris shed by Comet Temple-Tuttle in 1933, consisting of larger than average particles, and this is what accounted for the spectacular display.
Several members of OASI observed the Leonids in 1998 and their reports are reproduced below. Observers in Suffolk were particularly fortunate with the weather: most of the UK was clouded out but East Anglia benefited from clear skies! Unfortunately, many would-be observers prepared to observe on the evening of 17-18 November and therefore missed the peak of activity.
Like most observers I made serious plans to observe the Leonids only on the night of 17/18 November, Tuesday night and Wednesday morning. However, on the night of Monday 16 November, Sue Brown planned to make a visual count and Nigel Evans was coming round to try some photography so I decided that I too should undertake some observations. Monday night was perfect: very cold, down to -4°C and completely clear.
With Sue counting and noting times of meteors, positions and magnitudes, my aim was to get some photos. I had two cameras mounted on my driven 36 cm telescope. Both used 35 mm slide film; one with a 24 mm lens and 400 ASA film set for 10-minute exposures and the other with a 17 mm lens and 1600 ASA film using five-minute exposures. The 24 mm camera had a rotating shutter system which gave 17 breaks per second.
Initially, at about 11.00pm, Nigel and I climbed the hill opposite my house to get a better view of the eastern horizon. Even with the sickle of Leo on the horizon and Regulus not yet visible, meteors started appearing in the sky so we knew to expect a special display. I left Nigel to take some pictures on the hill while I went back to my cameras in the garden and began the night's exposures.
What a night! This was easily the best meteor shower that I have ever seen; there were so many bright meteors. Then, at about 00:45 UT, there was a tremendous streak of light almost overhead. I wasn't looking up when it started but it illuminated the garden and I looked up just in time to see a dazzling fireball. After the initial shock I could see the eerie green glow of the train hanging in the sky. I rapidly finished one exposure and started another to capture the train. I had a third camera in reserve, mounted on a tripod, to aim at any trains that appeared. I fired off some shots with this camera over the next 15 minutes during which the train was visible, twisting and distorting in the high atmosphere. Luckily both driven cameras also captured the fireball. While the train was visible, instead of clean breaks from the rotating shutter, the gaps were filled with its green glow. The train started in Auriga, passed just north of the Pleiades and ended in Aries near Saturn. After about 10 minutes it had spread out so much that it covered an area the size of the "W" of Casseiopea.
As the night progressed we saw many more bright meteors and captured some on film. As the radiant rose I turned the 24 mm lens towards it and began to capture two, three, four, five and even six meteors on a single 10 minute exposure! By now, several meteors per minute were visible and many had terminal flares which lit up the sky. Sometimes the meteor itself wasn't visible because of trees but the terminal flash could easily be seen.
Even after five hours spent outside in freezing temperatures I wanted to carry on observing but knew that I wouldn't survive a day at work if I did. So reluctantly I packed up and grabbed a couple of hours sleep. Had I thought a little more about what I had been witnessing I would have stayed up till dawn! The best photo that I took was my very last one, showing five meteors in 10 minutes. With hindsight it was clear that the shower was becoming more intense as the night went on; but the combination of tiredness and cold obviously clouded my judgement and I lost forever the extra couple of hours observing before twilight!
The second night, 17-18 November, was totally different! We set-up our equipment in expectation at 11.00pm and then...... Nothing, virtually no meteors at all! After about an hour and a half we decided that a second night out in the cold wasn't necessary, the 1998 Leonids were over!
I managed two watches during the 1998 Leonids, the first from 00:30 to 01:30 UT on Tuesday 17 November and the second from 04:40 to 05:25 UT on Wednesday 18 November.
The Tuesday morning count yielded a total of 71 meteors which included five sporadics. The majority of shower meteors were brighter than magnitude -2, most leaving trains. I saw a fireball at 00:51 UT in Taurus, magnitude circa -10 or -12, with a train visible to the naked eye for 17 minutes, drifting some 5° west. (Note: this appears to be the fireball captured on film by Mike Harlow, above.)
The second watch on the Wednesday yielded only 15 meteors, 10 shower and five sporadics, with none brighter than magnitude 0.
I regret not staying up longer on the Tuesday! By other reports I've seen, the counts increased dramatically towards dawn. In the brief few minutes that I spent watching the sky at 05.45 UT that morning (whilst cleaning the ice from my car windows!) I saw meteors at the rate of three or four a minute. I had to get some sleep though.
I journeyed with a group of friends from Bristol Astronomical Society (BAS) to darkest Exmoor to view the Leonids. We enjoyed some brilliantly clear nights! We had a long clear spell around midnight on Friday 13 November (despite it pouring with rain when Nicky and I arrived at 10.30pm) and we also had clear nights on the following Sunday and Wednesday. We saw a moderate number of Leonids on Sunday and Wednesday nights. We also saw a lot of sporadics, particularly on Sunday.
Meanwhile, in Bristol, on the evening of Monday 16 November it was cloudy until after 2:00 UT (on 17 November). Many people assumed that it would remain cloudy all night, but, in fact, it cleared up and several people in Bristol saw bright fireballs of around magnitude -10 in the early hours. One observer (in urban Bristol) had gone to bed, but when he woke up (possibly around 3:00 UT) he saw something like a flashgun which came from a small crack in the curtains. When he looked out of the window he saw several bright fireballs in the space of a few minutes. Several observers reported hearing cracking noises.
One person in Bristol and one person in Ipswich reported seeing a meteor during the day on Monday.
I observed with my wife for a couple of hours around the predicted peak time at 17:00 UT on 17 November. We observed from our back yard under many layers of warm clothing! We noted just 15 or so meteors per hour; some of them were brilliant.
Mike Harlow, Michael Barriskill, Pete Richards & Ken Goward