Wed 11 Aug 93 18:18
By: Don Allen
To: All
Re: WARNING ABOUT PERSEIDS

 * Forwarded from "ASTRONOMY"
 * Originally by Dan Cote
 * Originally to All
 * Originally dated 8 Aug 1993, 18:49

  Hi there you all,
    Please read IAU Circular No. 5839 that was kindly posted
to us by Edward Locke.

    To our misfortune, this IAU circular was misinterpreted 
by MANY newspapers around the world. I was shocked this morning 
to read in our local newspapers that Perseids won't be at the 
annual rendez-vous this year! What a crap!

    The paper (Le Soleil) has a translated (and mostly 
interpreted) story that came originally from San Franscisco and 
the Toronto Globe and Mail. The title (Beautiful Perseids, this 
is for next year!) says it all. The arcticle leave an impression 
to the reader that Perseids won't be here this year and that all 
the publicity that was made around this event was to be ignored.

  The IAU circular state :

  [On the assumption that the 1991 and 1992 events were produced 
by the ejection of material from P/Swift-Tuttle in 1862,] 
astronomers [calculate that the maximum activity in 1993 could 
be at any time between Aug. 11.92 and 12.06 UT, and that there 
is more likelihood of an actual Perseid storm in 1994.]

    IAU Circular 5839 is talking about possible facts based on 
an assumption. THIS COULD BE TRUE AND THIS COULD BE FALSE. We 
still don't know very much about the dynamics of comet P/Swift-
Tuttle to have good predictions on the storm. Anyway, the 
erseids WILL BE HERE THIS YEAR.  In their baddest appearance, 
Perseids are still the most spectacular meteor shower we may 
observe and this year WON'T BE DIFFERENT than previous years 
where we have seen an increasing number of meteors around the 
calculated peak. IAU circular 5839 also leaves us a "wide margin 
for interpretation" in the following passage :

  Another astronomer [... indicates that any real storm in 1993 
would be likely to occur close to t_0.  In any case, comparison 
with 1863 ... when t_0 = 1863 Aug. 10.68 UT occurred some 11 
months after the comet passed its node, suggests the potential 
for impressive Perseid activity up to fully 0.7 day after t_0.]

Actually, this makes the whole thing much more different than we
expected. IAU circular says that the peak of a storm could happen
between August 11, 22h UT (August 11, 18h EDT) and August 12, 
01h30m UT (August 11, 21h30m EDT). Another _assumption_ based on 
the last passage of the comet says that the storm COULD happen 
sometime after the calculated peak. It is said here to be around 
0.7 day after the calculated peak. THIS IS 16 HOURS OFF the 
calculated time!

  Now, here are my predictions :

  1 - We still can't say with a fair accuracy if there will be a 
      meteor storm or not.

  2 - We will have a Perseid shower this year. This one will be 
      AS NICE and AS BEAUTIFUL as those we had in the past years.

    For you guys who made (of this year's Perseids) a big show to
 promote your astronomy club, I have to say "Go ahead! And show 
them a meteor shower!". Don't be disapointed if the storm doesn't 
show up. But remember that astronomers just said that the storm 
could happen sometime between the evening of August 11 and the 
afternoon of August 12 with a _possible_ peak on the evening of 
August 11 or... in 1994.

  Would you like to be like those people who missed the Leonids 
1966 storm?  Don't let you be fooled by assumptions, they are 
often bad leaders...

  Clear and dark skies!
                       Dan
                       ICAoS Coordinator
                       RASC, Quebec Centre

 -- SPEED 1.30 [NR]: S.R.A.C. Centre de Quebec - R.A.S.C. Quebec Centre

 * Origin: ** UFO Moderator, Head Bouncer & Jaster Blaster ** (1:123/26.1)