From: Joe Rao
Date: Thu, 21 Nov 2002 11:57:21 EST


LEONIDS 2002

    The four-revolution dust trail of Comet 55P/Tempel-Tuttle was somewhat
late in encountering the Earth on Tuesday morning, November 19.  Revised
predictions by Rob McNaught and David Asher gave 10:34 UT as the time of the
peak.  Esko Lyytinen and Ton Van Flandern forecast the peak for 10:40 UT.  It
appears that the peak actually came within a minute of 10:48 UT, or 8 to 14
minutes later than expected.

    Interestingly . . . a prediction issued only several weeks earlier by
Jeremie Vaubaillon, at the Inst. de Mecanique Celeste et de Calcul des
Ephemerides (France), indicated that the 4-rev. peak would arrive at 10:47 UT
-- apparently just one minute earlier than what actually happened!

    The four revolution trail apparently consisted chiefly of very small
particles which produced a meteor display much fainter than what was observed
with this same trail in 2002.  There were far fewer fireballs and bolides
reported in 2002 and it appears that many of the meteors were of second and
third magnitude.  This sharp peak apparently lasted no more than 15 to 20
minutes in duration, centered on 10:48 UT.

    As such . . . moonlight, radiant altitude, local sky conditions and
twilight all played key roles in what observers saw . . . or did not see.

    Those blessed with excellent seeing and transparency conditions, along
with a very high radiant position and with the moon low in the west and
little or no twilight to contend with, saw a burst of 10 to 20 Leonids per
minute (on average). I've received many such reports from the Carolinas down
through Florida of people seeing just such a Leonid display.

    Along other parts of the US East Coast, a scattered-to-broken layer of
mid-to-high level cloudiness likely obscured a number of the fainter streaks.
 Also, in other parts of the country, similar adverse sky conditions
(combined with the bright moonlight) cut in significantly to the overall
numbers that were seen.

    In addition, the 8 to 14 minute delay in the predicted peak time meant
that twilight conditions had advanced enough over the East Coast of the US,
to allow the sky to brighten -- in some cases, as in the Northeast States --
to a considerable degree.  As a result, many of the fainter meteors were lost
in the brightening dawn glow.  Those who had to deal with such weather
problems, as well as the increased twilight effects, probably came away
feeling that the "big meteor shower" that had been heavily promoted in the
media never came off!

    In reality, however, the Leonids pretty much came off as anticipated.
During the 15 to 20 minute peak, those observing with very favorable
conditions saw meteors falling at the rate of 600 to 1200 per hour!

    Again, the only drawback was the fact that many of the meteors were
relatively faint . . . at least compared to the dazzlers that were observed
in 2001!

    Those who heard reports in their local media that " . . . up to 6,000
meteors per hour" would be visible with this year's Leonids, did not listen
carefully enough to the disclaimer (if it was mentioned at all) regarding the
nearly full Moon; and that almost certainly only a fraction of those promised
high rates would be visible thanks to the brilliant moonlight!  This factor
was stressed several times in my Leonid article in the November 2002 S&T.

    While a number of people saw an excellent Leonid show, the numbers of
those who were disappointed or dissatisfied (or just downright angry) seem
(at least to me) to be much larger.  Hell . . . even David Letterman
complained ("Any of you guys wake up to see that big meteor storm they were
predicting?; Well . . . I fell for it too.")

    Yet, when the final analysis of this year's display are made available by
the IMO, I would not be the least bit surprised to hear that the final ZHR
tally (after all the suitable "corrections" are made) will be somewhere in
the 2,000 to 5,000 range.

    No doubt, this will go down in astronomy annals as "The Leonid Meteor
Storm that almost nobody saw!"