- A fine display of shooting stars is underway and peaks
overnight Wednesday into early Thursday morning. Astronomers expect the
2004 Perseid meteor shower to be one of the best versions of the annual
event in several years.
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- Watching meteors requires no special gear -- telescopes
and binoculars are of no use. So anyone in the Northern Hemisphere with
clear skies could see some "shooting stars."
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- Seasoned meteor watchers suggest finding a dark location
away from city and suburban lights, if possible. Some brighter streaks
will be visible from cities but urban lighting will drown out the bulk
of them. Take a blanket or lounge chair so you can lie back and scan as
much of the sky as possible, experts say.
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- Perseids can appear anywhere in the sky, but if traced
back they will appear to emanate from a point in the constellation Perseus,
which rises in late evening in the East and is high overhead in the wee
hours before sunrise.
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- When to watch
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- During peak times, and for moments or perhaps hours at
a stretch, the Perseids could generate about a meteor every minute for
viewer's in dark locations. Sporadic brief bursts of a few in a single
minute sometimes occur.
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- A good display could begin Wednesday night starting around
9 p.m. local time for those with dark skies. Because of the celestial mechanics
involved, a few "earthgrazing" meteors could emerge from near
the horizon in these late evening hours and race horizontally across the
sky.
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- The hours from 2 a.m. until dawn local time Thursday
will be the best. That is when the side of Earth you stand on faces the
oncoming stream of debris that creates the shower. Like an ornament on
the hood of a car, a predawn viewer sees bits of ancient comet dust being
scooped up by Earth's atmosphere as the planet plunges on its orbital course
around the Sun. Nighttime meteors have to catch up to the planet.
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- As a bonus Thursday, a thin crescent Moon will appear
near Venus in the eastern predawn sky. Venus is unmistakably bright, outshining
all other stars and planets right now.
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- Unlike last year when a Full Moon outshone many Perseids,
this year the thin Moon won't be much of a hindrance.
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- Behind the shower
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- The Perseids are the result of stream of debris in space
laid down by comet Swift-Tuttle, which orbits the Sun every 130 years and
spends most of its time in the far reaches of the solar system. On each
pass inward, bits of dust -- mostly the size of sand grains but sometimes
as big as marbles -- boil from the comet's surface. When Earth passes through
the debris each August, the bits are vaporized in the atmosphere.
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- "Expect 40 to 60 meteors per hour, some of them
bright," says Bill Cooke, a researcher at NASA's Marshall Space Flight
Center.
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- An even busier shower might await skywatchers in Europe,
Africa and Asia. Astronomers predict Earth will pass through a dense portion
of the stream at around 4:50 p.m. ET (20:50 GMT) on Wednesday. The Perseids
typically do not put on much of a show south of the equator.
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- The Perseids have been ramping up for about two weeks.
The activity will drop off rapidly after Thursday morning but stragglers
will appear for up to a week. Other meteors not associated with the Perseids
are also visible this time of year.
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- © 1999-2004 Imaginova Corp. ALL RIGHTS RESERVED.
http://www.space.com/spacewatch/perseid_news_040811.html
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