Royal Astronomical Society Press Notice

Date: 18 November 1999

For immediate release

Ref. PN 99/35


Dr Jacqueline Mitton

RAS Press Officer

Office & home phone: Cambridge ((0)1223) 564914

FAX: Cambridge ((0)1223) 572892


RAS web:


Professor Mark Bailey (

Armagh Observatory,

College Hill,

Armagh, BT61 9DG

Tel: 028-3752-2928, Fax: 028-3752-7174


on the Armagh Observatory Leonid web site:

on the European Southern Observatory web site:


Preliminary results from observations of last night’s Leonid meteor storm indicate that the prediction made by Dr
David Asher of Armagh Observatory and Rob McNaught of the Australian National University of a strong shower
peaking at around 2.08 a.m. UT (or GMT) were spot on — even to the extent that faint meteors would dominate
compared with the exceptional fireball display last year. This is the first time that astronomers have succeeded in
making such an accurate prediction of a meteor storm.

The peak rate of meteors is more difficult to predict than the time of maximum. Asher and McNaught had been cautious
with their public statements, but had reason to believe from their latest work that it could be higher than the 20 per
minute they had been suggesting. The preliminary observations seem to show that a higher rate did indeed occur.

“We are delighted with this vindication of the method used by Rob and David”, said Professor Mark Bailey, Director of
the Armagh Observatory. The only cause for regret in the UK today was that most of the country was blanketed in cloud
at the crucial time.

Attention will now be focussed on their prognostications for the next three years. Next year (2000), they predict,
will be “the calm before the storm”: the Earth will pass through the centre of the broad meteoroid stream without
passing directly through any of the dense, recently ejected dust trails. “It’s rather like the ten-pin bowler who,
having left half a dozen pins standing after the first shot, bowls clean through the gaps with the second shot” said
Professor Bailey.

Next year’s observations will, however, be important for gathering further observational information about the
location and extent of the dust trails. The Earth will pass, for the first time ever, through the outskirts of the dust
trail deposited when Comet Tempel-Tuttle made its appearance in 1866. This trail could prove to be denser than

The showers in 2001 and 2002 are expecte to be dominated by close encounters of the Earth with this 1866 trail.
Predictions based on their present model lead to zenithal hourly rates well in excess of 10,000 meteors per hour.
Actual observations in 2000 should help to determine whether this is correct, or an under- or over-estimate.