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(meteorobs) Re: trains and trails
Ed.
A very interesting and useful set of definitions.
The trains/trails descriptions are interesting also because of what one sees
in telescopic views of meteors.
Quite often when observing deep sky objects, usually using around 180X on a
20" telescope, I see meteors crossing the field of view. Quite often these
produce a short lived trail of a few seconds duration. As these form
slightly behind the meteor, they seem to puff outward rapidly but visibly to
form an almost parallel sided trail of very roughly 1 minute of arc or so in
width. Further expansion is much slower.
I'm interested also to see that the sodium yellow line is important in the
spectra of trails as where I have seen any impression of colour it is
orangeish. I cannot recall seeing in these telescopic objects a greenish
trail as one might expect if the auroral oxygen line was being involved.
Does anyone else have any similarhigh magnification telescopic meteor
obsevations? It would be intersting to compare notes.
Nick
>Date: Thu, 18 Oct 2001 18:17:58 -0700
>From: "Ed Majden" <epmajden@home.com>
>Subject: (meteorobs) Fw: trails, trains, etc
>
>
>
> 2. SHORT-DURATION METEOR TRAINS (OR TRAILS)
>
> Luminous trains left behind the meteor for up to about 3 seconds. They are
>often observed visually and by video techniques in fast
> meteors like Perseids. They are present also in faint meteors, of
> magnitude +4 or so. In fact the ratio of the train/meteor brightness is
> larger in faint meteors than in bright meteors. The train is not
> connected with the meteor. In fact, it forms at a given position
> with some delay after the meteor passage. The the train is also
> considerably shifted to higher altitudes than the meteor which produced
> it.
> The short-duration trains are formed by only one spectral line,
> the green auroral lines of neutral atomic oxygen at 5577 A. This
> is a forbidden line. The luminosity is produced (very probably) by
> the atmospheric oxygen.
>
> 3. PERSISTENT LONG-DURATION METEOR TRAINS
>
> Luminous trains left behind the meteor for from 3 seconds up to
> differently from case to case. The spectra show both continuous
> or quasi-continous radiation and atomic lines. The most important
> and most persistent line, common for all spectra, is the sodium line
> at 5893 A. This suggests that the long-living luminosity is due
> to similar mechanism which produces the sodium airglow.
Nick Martin, Bonnyton House, By Ayr, Ayrshire KA6 7EW ,Scotland, UK.
Latitude 55 24'56" Longitude 4 26' 00".
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