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(meteorobs) organic meteoroids
> Duncan Steel, an astronomer with Spaceguard Australia in Adelaide, has thrown
> another variable into the equation. If his model of the chemical composition of the
> Leonid meteors is correct, attempts to observe the approaching meteors may detect
> only a few per cent of them.
>
Dear Sirs,
I have not read the Duncan Steel's article yet, but from what
I know about the meteor spectra I would say the following:
Yes, most of the luminosity of meteors in the visual light
comes from the lines of sodium, magnesium, iron and other
inorganic elements. So, hypothetical meteoroids composed
only from the organic material would certainly produce fainter
meteors than "normal" meteoroids of the same mass. On the
other hand, I doubt that the organic meteors would be completely
invisible, especially if they were so fast as Leonids (71 km/s).
This is because:
- Organic material can produce radiation of molecules like
CN, C_2, CH, OH.
- Fast meteors induce the atmosphere to radiate. Although
bright lines of nitrogen and oxygen lie in the near-infrared,
there are bright visible nitrogen bands.
- Even faint fast meteors often exhibit trains of duration
of about 1 second produced by the forbidden oxygen line
at 5577 A of atmospheric origin.
As far as I know, no spectra corresponding to organic
meteoroids were reported up to now, although they
may have been simply discarded as "poor spectra".
I agree that such meteoroids may exist and may
be more abundant in fresh cometary ejecta. The more
reason to do a careful faint meteor spectroscopy during
the forthcoming Leonid outburst. Although this may be too
late for the satellites. But as for the number of meteoroids,
I am not so optimistic (sorry, skeptical).
Jiri Borovicka, Ondrejov Observatory
borovic@asu.cas.cz
> Author: Robert Matthews
> New Scientist issue 3rd October 1998
>
> PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS ARTICLE - THANK YOU
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