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(meteorobs) Re: LINEARID meteor shower in July?
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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