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Re: (meteorobs) Re: LINEARID meteor shower in July?
Wow, this system is amazing. Runs all night long and effortlessly
records every meteor for a perfectly accurate statistic and shower
association!
But, just like LINEAR put comet hunters out of business, this is
doubtless the beginning of the end for visual meteor observing :(
Mike
On 18 Jul 2001, at 6:58, Rob McNaught wrote:
> The predicted peak for meteors from C/2001 A2 (LINEAR) should have
> occurred around July 17.7 UT; a few hours ago. The radiant set from
> here in the early evening, before I got my video set up, but it rose
> above the horizon again for the last 70 minutes of observation before
> morning twilight.
>
> There was considerable interference by cloud in the latter half of the
> night, but the following numbers were recorded by MetRec
>
> UT SPO CAP SIA PAU SDA NDA PHE LIN
> 09:55->14:00 52 18 13 3 4 2 0 0
> 14:08->19:55 38 8 9 7 5 5 4 1
>
> Totals 90 26 22 10 9 7 4 1
>
> Clearly there was no major outburst, and the single LINEARid recorded
> could just be a chance alignment. It occurred at 19:19:39 UT and was
> 32 consecutive frames (1.3 seconds), bright (around mag 0) and a dustball,
> as one might expect from fresh cometary ejecta. It was already a
> streak of disintegrating dust on entering the field and continued to
> fade and dissipate as it crossed the field. The radiant used was
> RA 108, Dec -23 (2000), Vinf 31 and this meteor passed 1.3 deg from
> this velocity corrected position with observed angular vel of 10.0 deg/sec
> compared to the predicted 12.4. A dustball would clearly have decelerated.
> Probably less than 1 meteor in 100 has such an appearance in my video
> recordings.
>
> I have a major problem believing this meteor was connected with the
> current apparition of C/2001 A2. A back of the envelope calculation
> suggests unrealistically large ejection velocities would be required
> of the order of 1 km/sec and at great distances from the Sun (a year or
> so from perihelion). However as this comet appears to have made a
> previous passage thru the inner Solar System, it _could_ be ejecta
> from that passage. Such a dust trail would be extremely stretched to
> the extent that it may barely be detectable. Tiny ejection velocities
> result in large differences in orbital period for near parabolic orbits.
> An equivalent segment of a one revolution old dust trail in the Leonids
> might occupy several months, but be several thousand years long for a
> near parabolic comet.
>
> Perhaps observers in New Zealand or elsewhere in Australia may mave seen
> some activity.
>
> Cheers, Rob
>
> Robert H. McNaught
> rmn@aaocbn.aaodot gov.au
>
>
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