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(meteorobs) Aries-Triangulids...Speeds and Trains
Aries-Triangulids...Speeds and Trains
I'd like to get back to the possible Aries-Triangulid radiant thread for a
moment. I have been puzzled over something. I've been trying to figure out if
the Slow to Medium speeds of the possible members of this radiant (as
reported by Kronk, Gliba and Sleeter...see WGN Dec 93 pg260) were all viewed
close to the "radiant" or were some an appreciable distance from the radiant?
As pointed out in Curries article in WGN Dec 94, the speeds for a possible
radiant from his data indicates speeds in excess of the Delta Aurigids (which
is 64kms...Very Fast), if viewed some distance from the radiant. If they are
both correct with their speed judgements based on where the meteors were
sighted and the speeds the meteors should appear to have if viewed somewhere
else, Then this indicates to me that all meteors were sighted probably within
10 degrees of a radiant. Thus appearing Slow or Medium...and very short( I
don't know how short the reported meteors were...but I'd expect path lengths
to be in the neighborhood of around 2 or 3 degrees at best). I've personally
never witnessed a shower were all members were so close to the radiant with
none viewed significantly far enough to perceive a Very Fast motion...if
indeed from a shower with Very Fast speeds. Based on the speeds reported,
and assuming that this "showers" entry speed is Very Fast, I would expect to
see some persistent trains of .5 second or longer to be sighted. From Kronk's
WGN article, I believe it indicates that Gliba reported 11 possible members
and Kronk and Sleeter together reported about 18. All 3 observers (Kronk,
Gliba and Sleeter) indicated the average magnitudes were somewhere between +3
to +5. Definitely within the range of not noticing persistent
trains...although some +3's might be expected to show .5 second train
durations. But there were 3 notable exceptions. I admit I'm dealing with
only 3 numbers here that may seem insignificant. But Gliba reported a -2 and
a +1. While Kronk reported a +1 also. I've been carefully keeping track of
my persistent train data with each of my meteor reports for several
years....that is determining the percentages of each shower and sporadics for
each nite. I've noticed that showers with Very Fast speeds, their overall
train percentage is close to 50%, while that of relatively Slow and Medium
speeds are near 10% or less. As examples, the 1996 Perseids were 43%. And
going back to 1995, my Perseids(VF) were 40% on Aug 13/14...my closest
significant nite to the peak. For other major showers in 1995 that I observed
on: Lyrids(F) 29%, three different nites for the Eta Aquarids(VF) 40%, 43%
and 36%, Sdot delta Aquarids(M) 7%, Leonids(VF) 62%, North and South Taurids(S)
combined 0%, and Geminids(M) 4%.(Very Fast = F, Fast = F, Medium = M, Slow =
S) As you can see, when the shower speed is Medium or Slow, my persistent
train rates are very low as well. and when the shower speed is high...my
train rates are high...around 50%. Just on the surface, if these meteors were
members of a shower with rates at 64 km/s or faster, I'd expect at least one
of them to have shown a persistent train of .5 sec or longer. I didn't see
any indication about trains being reported. It's possible that they were not
indicated anywhere or not recorded during the actual observation. Now only
going back to my recollections here, Meteors of Very Fast showers that appear
very close to the radiant and are of magnitudes of about +2 or brighter
seemingly nearly all leave a visible persistent train. With foreshortening
strongly occuring real close to the radiant, Persistent trains should be
easier to detect for Very Fast meteors. When you all watch for the Leonids
next week, keep this in mind.
George Zay