(meteorobs) LEONID METEOR OUTBURST IN THE OFFING?

[Skywayinc at aol.com]

November 13, 2006

Contacts:
Alan MacRobert, Senior  Editor
617-864-7360 x151, amacrobert at SkyandTelescope.com
Marcy  McCreary, VP Mktg. & Business Dev.
617-864-7360 x143,  mmccreary at SkyandTelescope.com

LEONID  METEOR OUTBURST IN THE  OFFING?

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* Note to  Editors/Producers: This release is accompanied  *
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Late  this Saturday night (November 18, 2006) a meteoric sky show could
break over  New York, New England, and eastern Canada. According to SKY &
TELESCOPE  magazine, the Leonid meteor shower -- which put on intense
displays from 1998  to 2002 -- could return for a brief, last-gasp reprise.

Every  mid-November, as Earth cruises along its annual orbit around the
Sun, we pass  through the Leonid meteor stream. Most parts of the stream
are sparse, so we  get only a very minor meteor shower (roughly 10 meteors
visible per hour).  But some parts of the stream are much richer. This
year, reports SKY &  TELESCOPE meteor expert Joe Rao, specialists predict
that we'll sail through  a narrow, dense filament of the stream. The whole
thing should last for only  about a half hour centered on 11:45 p.m.
Eastern Standard Time on Saturday  night, November 18th.

In North America, only New England, easternmost New  York State, and
Canada's provinces from Quebec eastward will be positioned to  catch the
possible display. Even in these regions, the meteors will come  skimming
into the upper atmosphere at a low angle. This means that the  numbers
you'll see even during an outburst will be relatively low, perhaps  one
every couple of minutes. However, the meteors that you do see  overhead
will be long, dramatic "Earth-grazers" skimming almost horizontally.  Even
one of these can be a sight to remember.

Bundle up warmly, find a  dark spot with an open view of the sky, lie back
on the ground or in a  reclining lawn chair, and just gaze up into the
stars. Any Leonids you see  will be coming from the northeast. Be patient.

The best place to watch  from is actually westernmost Europe. Here the
shower will happen just before  the first light of dawn on Sunday morning;
the predicted time of the shower's  maximum is 4:45 a.m. GMT on November
19th. This side of the world will be  facing more directly into the
oncoming shower, so the meteors will fall more  nearly straight down, and
the observed numbers should be  greater.

Background

The Leonid meteoroids are  bits of debris shed by Periodic Comet
Tempel-Tuttle, and they continue to  travel in a broad stream along the
comet's orbit. Every 33 years the comet  passes through the inner solar
system, warms up in the heat of the Sun, and  sheds a new filament of
debris, adding to the general meteor stream. When  Earth encounters one of
these dense new filaments (which haven't yet had time  to disperse very
much), we can get a very strong but short-lived meteor  display.

This tends to happen around the years when the comet itself is  passing
through. The comet's most recent return happened in 1998, so you  might
expect that by 2006, all activity beyond the 10-per-hour background  would
be over. But experts predict maybe not.

The reason goes back  several decades. On the morning of November 17, 1969
-- three years after a  historic Leonid storm in 1966 -- an unexpected
burst of Leonid activity broke  over eastern North America. Some observers
reported seeing an average of two  to four meteors per minute. What had
caught observers off guard was Earth's  passage through a thin, relatively
dense ribbon of dust and debris that had  been shed by Comet Tempel-Tuttle
in 1932. The densest part of the ribbon was  less than 30,000 miles (48,000
kilometers) thick. Earth, traveling in its  orbit at 18.5 miles per second,
swept through it in only about a half  hour.

In 1999 Robert McNaught and David Asher published a paper on Leonid  dust
trails in the meteor journal WGN and cited the case of the 1969  outburst.
They forecast that in 2006, Earth will encounter a follow-on  section of
that very same dust trail from 1932. They predict that this  year's
encounter will be centered on 4:45 Universal Time (GMT) Sunday  morning,
November 19th.

Other leading meteor forecasters, such as Tom  Van Flandern of the United
States, Esko Lyytinen of Finland, and Jeremie  Vaubaillon of France, later
confirmed this encounter with the 1932 rubble  trail, and their predicted
times match McNaught's and Asher's to within a few  minutes, SKY &
TELESCOPE reports.

So another short-lived outburst  seems probable -- but it's unlikely to be
as intense as in 1969. That year's  encounter came about 4.5 years after
Comet Tempel-Tuttle passed closest to  the Sun. This year it's happening
almost 9 years after the comet last swept  through. So we'll likely pass
through a sparser region of the 1932 rubble  trail. A reasonable guess is
that the resulting display will be about half as  strong.

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You may download the graphics and read the captions in the  online version
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