[Prev][Next][Index][Thread]

(meteorobs) 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        |
*--------------------------------------------------------------------------*