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(meteorobs) FWD: CCD image of a meteor --- initial radius


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Date: Thu, 18 Jul 1996 11:37:59 +0200 (MET DST)
From: "Cis.Verbeeck" <verbeeck@uia.ua.acdot be>
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To: imo-news@hrz.tu-chemnitzdot de
Subject: CCD image of a meteor --- initial radius


I read the following message in sci.astro. I thought some people might be 
interested in this.

Cis Verbeeck

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From: dwittman@acme.as.arizonadot edu (David Wittman)
Newsgroups: sci.astro.research
Subject: meteors
Date: 9 Jul 1996 15:48:57 GMT
Organization: University of Arizona, Tucson, AZ
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Keywords: solar system


Some time ago, believing I had captured an image of a meteor with a
90" telescope and CCD, I posted a question here about whether such
images are rare enough to be useful to meteor researchers.  I thank
the people who responded and put me on the right track.  There are
several Web resources; in particular, the International Meteor Society
is at http://www.tu-chemnitzdot de/~smo/imo/index.html, and you can find
links there to experts at various institutions.  I got in touch with
Robert Hawkes at Mount Allison University, whose comments are
reproduced below with his kind permission.  I am making my image
available at http://acme.as.arizonadot edu/~dwittman/meteor.gif.  The
field of view is 5 arcminutes, and the 16-bit original suggests a very
faint, diffuse extension of the trail across the entire field which is
not apparent in the 8-bit GIF format.


>(a)  Is it a meteor?  I would think that it is most probably a meteor (with
>some possibility of a meteor-like small piece of re-entering space junk).
>The diffuseness and irregularity looks like a signature of a crumbling (or
>dust cluster) meteor. Unless it is a very fast, very faint comet (see
>below). 

[Dr. Hawkes didn't know at the time that I had taken another image
immediately afterward which showed nothing, thus putting severely high
lower limits on its speed if it had been a comet--like 5-10 minutes of
arc per minute of time. --DMW]

>(b)  Is it useful to meteor scientists?  Yes.  I am quite sure that high
>resolution documented meteor events are very rare, and this would help one
>to define better the ablation mechanism for faint meteors, and also the
>width of meteor trails, important because of the "initial radius" problem
>of radar meteors, is defined better from such work.  By the way, the
>reference to Hawkins and Whipple's work on using telescope images to set
>limits on the width of meteor trails is: Hawkins, G.S. and Whipple, F.L.,
>1958, Astr. J., 63, 283.  It is very old now, but one paper on the initial
>radius of meteor trains (looking at spinning induced dispersal of grains)
>is a paper I did back in 1978 near the end of my Ph.D.  - Hawkes, R.L. and
>Jones, J., 1978, MNRAS, 185, 727.   Also, a recent paper which we did on a
>(much brighter and more spread) meteor cluster is Pieres, P.A. and Hawkes,
>R.L., 1993 WGN: Journal of the International Meteor Organization, 21,
>168-174, "An unusual meteor cluster observed by image-intensified video".
>These references reflect the biases of my personal interest in your event -
>i.e. to nail down the width of (at least one) meteor trail with excellent
>precision, and to use it to study clustering of faint meteors (it is also
>interesting that our studies have yielded very little wake, longitudinal
>spreading, of faint meteors - a result which surprised us - I can send
>references if you like).
>
>I did try to sort through to find somewhat similar objects in the
>past.  In Corliss' book (not highly regarded by some, but likely to
>report such events).  There is one such event which might be similar
>(pg. 523).  It reports a fast-moving object (moves one minute of arc
>every 15 minutes), and has the appearance of a comet.  It was
>photographed from Turku, Finland on March 12, 1942 and confirmed by
>the Schmidt at Lowell Observatory. It was 13th magnitude. Have you
>been able to check for a fast moving, faint comet (i.e. in some plates
>along the line of apparent motion at later times, if they
>exist??). The paper was in Science, April 3, 1942.
>

- --
David M. Wittman                  God made everything out of nothing.
dwittman@as.arizonadot edu            But the nothingness shows through.
Steward Observatory                                    --Paul Valery
University of Arizona

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