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Re: (meteorobs) Ephemerides for Perseids
Stop Light Pollution! <GLIBA@grossc.gsfc.nasadot gov> asked:
> Anyone out there know the UT of the traditional Perseid peak, and the
>early IMO peak of the post Swift-Tuttle years?
Hi, George. In answer to your question about the traditional and "outburst"
maxima: The following two messages were sent to the imo-news group (and to
meteorobs) some time ago, with about a month and a half between them. Both
messages are forwarded verbatim from Casper ter Kuile of the IMO:
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Date: Sat, 04 May 1996 22:01:11 +0200
To: betlem@strw.leidenunivdot nl, m.cdot delignie@research.kpndot com,
peter@max.arc.nasadot gov, delpsurf@cistrondot nl, jvtleven@interdot nldot net,
pvmilnwk@boxdot nl, breukers@pidot net, mcavanvliet@pasti.stm.tudelftdot nl,
mottink@interdot nldot net, caroos@pidot net, C.F.Johannink@home.cnt.antennadot nl,
rjbouma@pidot net, bettonvl@fys.ruudot nl, neyts@worldaccessdot nl,
poerinku@worldaccessdot nl, p.m.koenraad@phys.tuedot nl,
gloudema@strw.leidenunivdot nl, e.a.g.hamers@max.fys.ruudot nl,
m.a.brentjens@fys.ruudot nl, j.hartman@hsbosdot nl, hhendrik@worldaccessdot nl,
imo-news@tu-chemnitzdot de
From: Casper ter Kuile <pegasoft@cc.ruudot nl>
Subject: Expected position of the 1996 Perseids peaks
DMS Information Circular
From: Marco Langbroek
Dutch Meteor Society (the Netherlands)
EXPECTED POSITION OF THE 1996 PERSEID PEAKS
Within a few months we will experience a very favourable Perseid meteor
maximum: it will be new moon on August 14! Below, some predictions on
when a possible 'new' peak will occur, as well as information on the
position of the main annual peak and other aspects of this coming return.
> THE 'NEW' PEAK: AUGUST 12, 0:30 UT +- 1h
The Perseid stream has shown 'near comet type' meteor outbursts (see [2])
in 1991, 1992, 1993, 1994 and 1995, connected to perihelion passage of the
parent comet P/Swift-Tuttle in 1992. With the exception of the 1993
outburst these outbursts lasted only short (<1.5 hours). The general trend
seems to be a diminishing peak ZHR from 1991 onwards. The outbursts
occured about 0.5 days before the regular annual stream maximum, but the
peak positions of the outbursts showed variation in solar longitude.
We are not sure if there will again be an outburst coming return, but
chances are certainly still good, though if it occurs it will not necessarily be
very spectacular. A slight enhancement of rates, with some nice bright
meteors, is very well possible. And who knows: with some luck, it might be
even more than a 'slight enhancement'....
We have a pretty good idea on when an outburst might occur, if it occurs.
The position of the peaks from 1991 to 1995 shows a nice pattern. Extrapo-
lated, and with an eye to the patterning in recurrent outburst phenomena
with other streams, we can expect it to occur near solar longitude 138.945
+- 0.5 degrees (B1950). This will be on August 12, 0:30 UT +- 1h.
This will be very favourable for western Europe, which will have the
radiant high in the sky at that moment, and a completely dark sky without
moon or twilight.
We strongly emphasize however, that observers should monitor a much
broader time-window than that mentioned above. This is only a PREDIC-
TION!!! Another reason to keep an eye open earlier and later that night
(besides for the obvious fact of gathering data from the annual stream
component, which is of course as important), is the suggestion by some that
last years more than one peak might have been operational (see the
December-issue of WGN).
THE ANNUAL MAXIMUM
The 'normal' annual maximum of the stream is located at solar longitude
139.49 +- 0.04 (B1950, [1]), which will be around 14h UT on August 12
this year.
Activity might be slightly above the average maximum ZHR of 84 +- 5
since we are experiencing a very deep minimum in solar activity at this
moment. Variations in solar activity have it's influence on the upper
atmosphere and introduce variations up to 20% in the annually observed
rates of streams, most notably for streams consisting of fast meteors like
the Perseids [1].
Due to the very favourable moon ephemeris, a large part of the Perseid
activity curve will be observable from August 8 onwards this year. I wish all
of you enjoyable observational nights!
- Marco Langbroek (Dutch Meteor Society)
Jan Steenlaan 46
NL-2251 JH Voorschoten
The Netherlands
[1] Jenniskens P., 1994: Astron. Astroph. 287, 990-1013
[2] Jenniskens P., 1995: Astron. AStroph. 295, 206-235
DMS-homepage: http://www.pidot net/~terkuile/meteors/dms.htm
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/ Casper ter Kuile, DMS, IMO, Delphinus GSM: +(31)-06-54723974 \
\ S-mail home: Akker 145, NL-3732 XD De Bilt, the Netherlands /
| Internet WWW-Homepage: http://www.pidot net/~terkuile/meteors/dms.htm |
/ E-mail home: pegasoft@cc.ruudot nl Voice home: +(31)-30-2203170 \
\ E-mail work: casper.ter.kuile@rivmdot nl Voice work: +(31)-30-2742647 /
*-----------------------------------------------------------------------*
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Date: Sun, 16 Jun 1996 02:06:37 +0200
To: betlem@strw.leidenunivdot nl, m.cdot delignie@research.kpndot com,
peter@max.arc.nasadot gov, delpsurf@cistrondot nl, jvtleven@interdot nldot net,
pvmilnwk@boxdot nl, breukers@pidot net, mcavanvliet@pasti.stm.tudelftdot nl,
mottink@interdot nldot net, caroos@pidot net, C.F.Johannink@home.cnt.antennadot nl,
rjbouma@pidot net, bettonvl@fys.ruudot nl, neyts@worldaccessdot nl,
poerinku@worldaccessdot nl, p.m.koenraad@phys.tuedot nl,
gloudema@strw.leidenunivdot nl, m.a.brentjens@fys.ruudot nl,
j.hartman@hsbosdot nl, hhendrik@worldaccessdot nl, kuiper@knmidot nl,
severin@knmidot nl, meteors@cnt.antennadot nl, hercunet@cucidot nl,
lanzing@edte.utwentedot nl, G.J.S.Cladder@sgz.utwentedot nl,
astro@groep.edith.antennadot nl, a.w.ploegmakers@cet.hendot nl,
pruppers_heuvelsland@pidot net, eddy@cis.HZeelanddot nl,
imo-news@tu-chemnitzdot de, meteorobs@latradedot com, zenit@astro.rugdot nl,
mathlenr@fys.ruudot nl
From: Casper ter Kuile <pegasoft@cc.ruudot nl>
Subject: REVISITED PERSEID 1996 PREDICTION
DMS Circular
(issued by Marco Langbroek, Dutch Meteor Society)
REVISITED PERSEID 1996 PREDICTION
Summary - a still very preliminary model on meteor outburst
mechanics suggests a time of peak occurence different from an
earlier prediction. If the model is correct (which remains to be
proved), remnants of the 'new' Perseid peak (the outburst
component) might occur near 5h UT (+- 1hr) on August 12
instead of near 0:30 UT as previously predicted.
***
Dear everybody,
Not so long ago we issued a prediction on when possible rem-
nants of the 'new' Perseid peak of last years might re-occur.
This prediction was based on simple extrapolation of the patter-
ning in peak postion, the decreasing shift in increasing solar
longitude over the last years.
However, things might be different and it might be that the quite
neat behaviour of the 'patterning' in the period 1992-1995 was
truly coincidental (!). Recently developed idea's, which are, let
me stress, however still in a very preliminary state, suggest that
for outbursts of streams originating from comets with 'longer'
periods and large inclination, the peak occurences are connected
to the shift of the solar system barycenter [1]. While the theory
has been developed for 'far cometary type' outbursts, the same
mechanics could be at work with the Perseid outbursts (which
are of 'near comet' type) since the encounter conditions between
Earth and cometary orbit are somewhat similar to those of 'far
cometary' type outbursts producing long period comets [1].
There seems to be indeed some tentative correlation between the
solar reflex motion and the peak solar longitudes of the Perseid
outbursts in the period 1991-1995 [2]. If the tentative correlati-
ons produced hold (which remains to be seen), this would
suggest a possible re-occurence (provided that 'fresh' dust of
comet Swift-Tuttle is still present near the cometary node this
year) of the outburst peak component around 5h UT (+- ~1h)
on August 12.
This is a time considerably deviant from that believed previous-
ly. Yet, be very cautious: all this theoretical grappling is still in
an experimental state, and their actual validity is yet to be
proven! On the other hand, the model has the advantage that all
peak positions of the previous years, including those of the pre-
perihelion years, fit in well untill now.
The message is, that a lot is still uncertain about the time at
which an outburst component (if any left) might re-occur and
that the odds might be at least as good for the USA as for
Europe this year. So, the best thing observers all over the world
can do is to start observations in early evening twilight and to
proceed untill morning dawn. However, don't be disappointed
when nothing happens around either 5h UT or 0:30 UT. In that
case, you just enjoy a very favourable display of the annual
Perseid stream. Good luck to all of you!
-Marco Langbroek (Dutch Meteor Society)
[1] Jenniskens P.: Meteor stream activity IV. Meteor outbursts
and the reflex motion of the Sun. Astron. Astroph. (in press).
[2] Langbroek M.: Perseiden houden de spanning er in. Radiant
18, nr. 4 (in prep.).
DMS WEB-site: http://www.pidot net/~terkuile/meteors/dms.htm
*--------------------------------------------------------------------------*
| Casper ter Kuile, Akker 145, 3732 XD, De Bilt, the Netherlands |
| Phone: (31)-30-2203170; GSM: (31)-6-54723974; E-mail: pegasoft@cc.ruudot nl |
| World Wide Web: http://www.pidot net/~terkuile/meteors/dms.htm |
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References: