[extropy-chat] Perseid predictions
pfallon at ptd.net
Thu Aug 5 14:26:08 UTC 2004
Here is the abstract and conclusion from the just-published WGN article on
the 2004 outburst by Lyytinen & Van Flandern
In 2004, August 11 at about 21h UT, the one revolution dust trail of the
Perseids parent comet Swift-Tuttle is calculated to pass within 0.0013 AU
from the Earth's orbit and we expect this to cause a moderately strong,
short outburst of mainly visually dim meteors. We have drawn conclusions
from our (Lyytinen, TVF) prediction model that has been quite successful in
predicting recent Leonids storms. We also discuss the possibility of
enhanced yearly rates because perturbations by Jupiter will now direct all
incoming Perseids meteoroids about 0.01 AU closer to the Sun, which allows
the possibility of Earth passing through the densest core of the yearly
With the Moon at waning crescent phase on August 11, observing conditions
for the 2004 Perseids meteor activity should be excellent everywhere.
Because the radiant is at a high northern declination (+58°), most northern
hemisphere observers may expect to see meteors throughout the night.
Observers will not want to be north of 60° latitude or so because of the
"midnight Sun" in summer. Nor will they want to be below about latitude -32°
because the radiant will never rise above their horizon.
Using techniques that have had considerable success in predicting the times,
locations, and rates for meteor storms and shower peaks for both Leonids and
Ursids, we expect that even the annual activity of the Perseids may be
better than normal this year. Observations possibly confirming this or
rejecting this will be valuable. This will help in mapping the stream and be
used in predicting what to expect in the next similar situation in the year
2016. Even before this, in the year 2009 the planet Saturn makes a similar
even slightly stronger 'dip' into the incoming meteoroids stream.
But as Figure 1 (below) shows, conditions for the following years will
revert to more typical meteor rates. Perseids activity this strong or better
is not predicted again until the year 2028.
In 2004, a possible meteor outburst of mostly fainter-than-average meteors
may be seen on August 11 around 21h UT, with the optimum time occurring at
20h 50m UT. That will be daylight hours for the Western Hemisphere, but in
darkness for most of the Eastern Hemisphere. Asia will be best situated for
observing this outburst. The full width of half-maximum rate is predicted to
last about 40 minutes.
Posted by Pat Fallon
pfallon at ptd.net
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