Electronic Telegram No. 1464
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CBAT@CFA.HARVARD.EDU (science)
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PERSEID METEORS 2008
     P. Jenniskens, SETI Institute, reports that the earth will cross the 1479
dust trail of comet 109P/Swift-Tuttle on Aug. 12d05h30m UT.  The trail is
distorted and dilluted, making it difficult to predict the expected peak
rate of Perseid meteors.  E. Lyytinen (Helsinki, Finland) has predicted a
peak rate of ZHR = 200 meteors/hr, after taking into account a scaling
factor based on the 2004 encounter with the 1862 dust trail (Jenniskens
2006, Meteor Showers and Their Parent Comets, Cambridge University Press,
p. 657).  In contrast, J. Vaubaillon (California Institute of Technology)
predicts no more than a weak enhancement between 04h00m and 06h30m UT,
and this may not stand out well from the normal annual Perseid shower
activity.  M. Maslov (Novosibirsk, Russia) confirms the encounter with the
1479 dust trail, calculating that ejection speeds of 4.8 m/s are sufficient
to move the dust into the earth's path.  He also expects an increase of no
more than ZHR = 2 meteors/hr, adding that this value may be underestimated.
In addition, Maslov has pointed out that Jupiter's perturbations will also
shift the annual Perseids closer to the earth's orbit, suggesting a slight
increase of rates up to ZHR = 110-120 meteors/hr.  Finally, a significant
enhancement of Peseid rates may occur from a 1-hour-wide 'filament'
component, predicted to peak around Aug. 12d01h UT (Jenniskens 2006, op.
cit., p. 661).  This peak time is uncertain by several hours.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2008 CBAT
2008 August 9                    (CBET 1464)              Daniel W. E. Green