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2003 Leonids

Started by Whitters, Nov 14, 2003, 04:32:00

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Whitters

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BAA electronic circular No. 00123            http://www.britastro.org/
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Observing Opportunity: 2003 Leonids



Active annually from November 15-20, the Leonids have attracted much
attention in recent years during the high-activity phase which attended the
perihelion return of their parent comet 55P/Tempel-Tuttle. Leonid rates
began to rise in 1994, with fine displays in 1995 and 1996, and the
remarkable fireball outburst seen by many in 1998. A brief (1-hour) meteor
storm, with Equivalent Zenithal Hourly Rate 3000, occurred in 1999, and was
followed by two separate sub-storm outbursts in 2000. The 2001 return was
marked by two interludes of storm activity, over North America (EZHR ca
2500) and the Pacific (EZHR ca 5000), as forecast by a model of the Leonid
meteor stream first developed by David Asher and Robert McNaught. This model
also successfully forecast storm peaks close to 2002 Nov 19d 04h UT and 2002
Nov 19d 10h UT, each reaching EZHR ca 3000.

   Now, almost five years 'downstream' from the parent comet, the
expectation is that further major Leonid outbursts are unlikely until the
2030s. A couple of recently-issued forecasts from professional sources
suggest minor Leonid enhancements near 2003 Nov 13d 17h UT (debris from
55P/Tempel-Tuttle's 1499 perihelion) and 2003 Nov 19d 07.5h UT (1533
debris), neither of which is well-timed for observers in the British Isles.
The first putative peak is unusually early - before the main annual activity
commences! - while the second might produce rates exceeding a Leonid per
minute.

    All the outbursts in recent years have been ascribed to distinct debris
filaments within the Leonid meteor stream. The general 'background'
population of the stream has also been somewhat enhanced, and may remain so
in 2003, providing a reasonable shower with observed rate in excess of 20
meteors/hr under clear skies from a dark site. While those seeking the
'glory' of witnessing a meteor storm will be out of luck, regular meteor
observers will surely find the Leonids a rewarding target this year,
particularly on Monday-Tuesday Nov 17-18 and Tuesday-Wednesday Nov 18-19.
Even in 'quiet' years, the Leonids produce reasonable numbers of bright
events with long duration persistent trains.

    The bad news is that observations will be hampered somewhat by a broad
waning crescent Moon: last quarter is on November 17d, and lunar positioning
could hardly be worse, with the Moon in Leo, and therefore above the horizon
whenever the radiant is visible. By directing the field of view away from
the lunar glare - towards the northeast, say -and hiding the Moon behind
local obstructions, visual observers should still be able to obtain some
worthwhile watch data. If nothing else, the glare won't be quite as strong
as in 2002, when the Leonids had to contend with a nearly Full Moon.

    The radiant, in the 'Sickle' of Leo at RA 10h 08m Dec +22o, rises
around 23h local time, and is highest in the latter parts of the night:
post-midnight watches are necessary, and the interval from 03h until dawn
will probably prove most productive.

    Reports of visual watches, carried out by the Meteor Section's standard
methods (outlined on http://www.britastro.org/meteor) will be welcomed at
the address below. As always, observers are asked to take particular care in
recording limiting magnitude conditions, and remember to record all
meteors - including Taurids and sporadics - seen during their watches.

    Moonlight has seriously restricted meteor work during the most active
showers in 2003, and will allow only a short window of dark sky for the
Geminid maximum on December 13-14. A glance at the Meteor Diary in the 2004
BAA Handbook should, however, assure observers that better times are ahead
next year!



Neil Bone

Director, BAA Meteor Section

'The Harepath', Mile End Lane, Apuldram, Chichester, West Sussex, PO20 7DZ

Email: neil@bone2.freeserve.co.uk





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BAA electronic circulars service.      E-mail: circadmin@britastro.org
Circular transmitted on  Wed Nov 12 22:29:47 GMT 2003
(c) 2003 British Astronomical Association    http://www.britastro.org/
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