[Prev][Next][Index][Thread]
(meteorobs) What I think I know (and don't know) ...
... about the upcoming Leonids outburst I have summarized in the lead
story of http://www.geocities.com/skyweek/mirror/227.html - here's an excerpt:
Confusion mounts over the 2001 Leonids meteor storm
The picture is not nearly as clear-cut as it had seemed
(see Update # 211): Although no one doubts the general
physics of meteor storms anymore, there is considerable
confusion right now about the details - which translates
to great uncertainty about whether there will be a big
Leonids storm this November at all and if so, whether it
will be best in East Asia & Australia or rather in North
America. All models published so far are based on the
famous dust trails that worked well in 1999 and 2000 and
apparently in the past centuries as well. But among the
four major groups or individual theorists working on
predictions for 2001, three markedly different results have
been achieved:
The classical result, basically the same for D. Asher
& R. McNaught as well as E. Lyytinen, has two
strong peaks of the meteor rate on Nov. 18, 2001, one
around 10 UTC with about 2000 meteors/hour and
the bigger one around 18 UTC with 6000 to 15,000
meteors per hour. As far as the CM has learned, none
of these authors have revised their predictions which
remain basically the same after the 2000 observations
(which were forecast correctly in time, though not
the maximum ZHRs).
A very different result has been obtained by B.
Cooke of NASA's MSFC who - taking into account
worldwide observations of the Leonids in 1999 and
2001 - comes to the conclusion that there will be
only one veeery broad and shallow maximum,
peaking at a mere 1300 meteors/hour around 13
UTC.
Again completely different is a model presented by P.
Jenniskens at the Meteoroids 2001 conference in
Kiruna earlier this month: He sees again two peaks,
at the times predicted by Asher, McNaught &
Lyytinen, but with the intensities the other way
around. He expects a whopping 32,000 meteors/hr at
the 'American' 10 UTC peak and only some 2000/hr
at the 'Asian' 18 UTC one. This model is work in
progress, however, the final paper hasn't been released
yet, and it is already being criticized, as the
CM has learned.
How can the same basic model yield three very different
results? The problem is that there has never been a
situation like in 2001 (or 2002) when the Earth is coming
rather close to certain dust trails, but several years after
the parent comet Tempel-Tuttle came by. Thus there is no
way of telling beforehand how much dust there is in the
trails so far behind. And there are also several very poorly
understood mechanisms that can shift the trails away
from the Sun (Cooke) or towards it (Jenniskens). While
the observations of the Leonids activity from 1998 to 2000
are excellent, the data for the decades and centuries before
are often poor or contradictory, and the 3D shape and
location of the trails are just not constrained enough.
And where does all that leave the eager observer of the
2001 Leonids storm, perhaps the last one for decades to
come (see Update # 222 story 7)? In the middle of
nowhere, unfortunately: There is only one small region on
the whole globe from where the Leonids radiant is above
the horizon and the Sun well below it at 10 UTC as well
as at 18 UTC - in the Polar Ocean between Eastern
Russia and the North Pole! Even airplanes would have a
hard time to catch both peaks under good conditions. Thus
a decision has to be made whether to position oneself in
the U.S. (Arizona is said to have the best weather
prospects in November) or Asia or Australia - and by
November 19 we will know which of the three models
listed above was correct ...
Daniel (still holding out for South Korea, by the way ...)
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html
Follow-Ups: