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(meteorobs) on being forward...

Dear Meteorobs folk

I would like to note that my comment in ccnet, re my P/2000 G1 LINEAR
thoughts having had 'the living daylights forwarded out of them", has led
some to feel that I was making a complaint.

This is not the case.  I am neither displeased nor pleased by the
forwardings, just simply bemused!

The comment was merely just a statement of fact, and to some extent worded
due to personal idioms of speech.

So if anyone should think I've been upset by anything re this, don't worry,
I'm not.

SOME METEOR STUFF

Right, after that 'off topic' bit, I suppose I ought to make some
recompense with some meteor stuff that's hidden in the depths of my poor
and much abused hard disk:-

The NEO 2000 BD19 seems to have a significant number of meteors linked to
it via orbital similarity as per the IAU photographic and radio databases,
despite quite some distance between closest orbital approaches [0.9 AU].
The apparent radiant lies in mid Virgo in mid Feb.  Initial attempts to see
if this had anything to do with the Virginid's complex proved fruitless.
Indeed, it now seems that certain highly eccentric objects [e>0.8] are
bound to have Feb radiants around the Virgo area due to simple geometric
effects.

Nevertheless, someone was kind enough to offer to look at more modern radar
data for any further evidence of meteoroid stream co-orbital with this
asteroid/defunct comet/piece of space debris.  That's still ongoing...


18D/Perrine-Mrkos' 1896 orbit shows some similarity with those for the
handful of photographic meteors that define the 'mu Pegasids' [sometimes
just Pegasids] outburst in 1952 [McCroskey & Posen, I believe].  There had
been a Jovian interaction for this comet just a few years before 1896 which
led to that orbit.

This comet's orbit has changed quite a bit over the years anyway, believed
due to 'non-gravitational' effects, and it was lost once only to be
rediscovered in the 50's and lost again!  Recent work by Sitarski which
takes these gravitational effects into account predicts a changeable orbit,
and a possible re-recovery in 2003.

The post-Jovian encounter 1896 orbit gives a predicted radiant somewhat
late compared to the actual date of the mu Pegasids [Nov 11/12].  These
meteoroids would have had to stay unperturbed in this orbit whilst the
comet's orbit evolved, but as the comet's recent orbital evolution is
suggested by some to be due more to non-gravitational effects [jets] than
planetary perturbations, this is not a problem. 'Jetting' comets given rise
to meteor showers, or ven outbursts, is not unknown.

[If one really wanted to push it one could try and make some claim re tidal
effects during the Jovian interaction making fresh volatile material
available on the comet's surface, one could, if one really wanted to push
it... ...but that's just pure conjecture, on ones part!]!

Due to the details of the 1896 orbit this would be a 'far-comet outburst'
type, using Jennisken's definitions, which seems a bit contradictory re
jetting etc.

Some orbital dynamicists somewhere are apparently looking into all this
[hopefully!].


Finally, C/1739 is the parent comet to the Leo Minorids.  This shower
itself is little known, and the cometary association very rarely noted in
comet-meteor shower lists.  It was actually first noted as the parent comet
in the actual discovery article for the shower itself [again McCroskey &
Posen!], and apparently even the legendary Denning had noted previously
that there ought to be a shower associated with this comet.

Yet as I say, though in the ALPO and IMO lists, the shower itself is rarely
mentioned.


Cheers

John

John Greaves
UK

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