Few sky shows in our lifetimes will come close to matching the
breathtaking, easy-to-watch 2001 Leonid meteor shower. Except maybe the
2002 Leonid meteor shower. Another storm is in store for Nov. 19, and
the main question is how much of it we will see.
Astronomers say a peak of activity expected over North America could
generate more than 40 shooting stars every minute. Europeans will be
treated to an even better display. Unfortunately, many of the fainter
streaks will be drowned out by a full Moon.
Colorado astrophotographer Gary Emerson captured the fury of the great
1966 Leonid meteor storm, the most spectacular storm of the 20th
Century. This image was taken over 20 minutes and records only the
brightest meteors. At the storm's peak, Emerson says he saw thousands of
meteors per second. "It was one hell of a show," he said.
The Leonids are an annual event caused by comet Tempel-Tuttle, which
orbits the Sun every 33.2 years and leaves behind a new trail of debris
on each pass. Most of this debris is no larger than a grain of sand, and
it vaporizes when it crashes through Earth's atmosphere.
Predicting the shower involves figuring out which streams of debris
Earth will pass through each year and how dense they will be -- how much
the stuff has spread out over decades and centuries as it wafts through
space.
The forecast
Forecasters generally agree that Earth will pass through two primary
debris streams in 2002.
The first stream could generate a peak rate of more than 3,000 shooting
stars per hour just before dawn over Europe and Africa on Tuesday, Nov.
19.
A second burst is slated to occur near dawn the same day over eastern
North America and is forecast to produce around 2,600 meteors per hour.
That's 43 per minute or nearly one each second.
Peak rates are typically observed in short, stunning bursts that can
last anywhere from 15 to 45 minutes, though they are expressed as hourly
rates.
The North American peak will also serve residents of the West Coast and
those in the middle, too, but the timing puts the best potential in the
East.
Meteor forecast is still in its infancy, however, and estimates for
exact timing and especially for the rates could change between now and
November. The date is firm, though.
Even if the forecasts are off the mark, the Leonids always provide some
sort of shower. The nights and mornings leading up to the peak are sure
to provide a handful of shooting stars and even fireballs, bright
mini-explosions that tend to take over the sky. And despite the Moon's
interference, there is cause for optimism in 2002.
"If you enjoyed them in a good sky last year, don't expect something as
good this year, because of the observing conditions," said meteor shower
forecaster David Asher of the Armagh Observatory. He adds, though, that
"if you missed them, and you've never seen a meteor storm in a dark sky,
you can expect an excellent display."
Tactics
Serious meteor watchers begin their Leonid observing in earnest two or
three nights prior to the peak, to gauge views and sky conditions and to
practice their spotting skills. With a full Moon looming, choosing a
good location is crucial.
The Moon will be just approaching its full phase, up all night and
setting in the west just before sunrise -- right when the peak activity
is expected in eastern North America.
Robert Lunsford, a seasoned meteor watcher with the American Meteor
Society, says the bright moonlight will be exacerbated in regions with
high humidity.
"Those under hazy skies will be at a distinct disadvantage as the
moisture will scatter that much more light," Lunsford explained
recently. A trip to the mountains can provide lower-humidity conditions.
"For those stuck in humid air, I would suggest using a tree or the east
side of their house to block the Moon."
Lunsford also recommends setting out an hour or more before prime time,
to practice a bit and to allow your eyes to fully adjust to the
darkness.
Mountain climbers
One group of long-time meteor watchers is heading to the mountains of
North Carolina, where they plan to use high peaks to block scattered
moonlight and improve their view by observing from deep canyon shadows.
Tom Van Flandern, a meteor forecaster who's helping to lead the
expedition, told SPACE.com that test observations have shown that during
a full Moon, twice as many stars can be seen from their chosen location
in the Appalachians compared with other sites. The group will start out
at a mid-elevation site. If the moonlight seems a problem, they'll move
to deeper shadows. If clouds threaten, they will try to climb above
them.
Avid amateurs are invited to join the journey, which is part of Eclipse
Edge Expeditions.
Van Flandern said the eastern location was chosen to coincide with the
pre-dawn peak of the shower, when the Leonid meteors will emanate from a
point high in the sky. Further west, this so-called radiant point will
be lower in the sky during the peak, so fewer meteors will be visible.
But, he said, observers "stuck" in the West or southwestern United
States should still see a strong shower.
The peak will occur shortly after midnight in the West and around 2-3
a.m. in the Midwest. For all North American viewers, the shower should
be worth watching from midnight to dawn.
This year's expected storm is the last in a series that dates back to
1999 for the Leonids. Beginning next year, things change dramatically.
No Leonid storms are predicted again until 2033.
Copyright 2002, Space.com
This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.