in late April Earth passes through the dusty tail of Comet Thatcher
(C/1861 G1), and the encounter causes a meteor shower--the Lyrids.
This year the shower peaks on Tuesday, April 22nd. Forecasters
expect 10 to 20 meteors per hour, although outbursts as high as
100 meteors per hour are possible.
appear to stream from the bright star Vega in the constellation
In fact, Lyrids
have nothing to do with Vega. The true source of the shower is
Comet Thatcher. Every year in April, Earth plows through Thatcher's
dusty tail. Flakes of comet dust, most no bigger than grains of
sand, strike Earth's atmosphere traveling 49 km/s (110,000 mph)
and disintegrate as streaks of light.
Lyrid meteors are typically as bright as the stars in the Big
Dipper, which is to say of middling brightness. But some are more
intense, even brighter than Venus. These "Lyrid fireballs"
cast shadows for a split second and leave behind smokey debris
trails that linger for minutes.
the shower intensifies. Most years in April there are no more
than 5 to 20 meteors per hour during the shower's peak. But sometimes,
when Earth glides through an unusually dense clump of comet debris,
the rate increases. Sky watchers in 1982, for instance, counted
90 Lyrids per hour. An even more impressive outburst was documented
in 1803 by a journalist in Richmond, Virginia, who wrote:
stars. This electrical [sic] phenomenon was observed on Wednesday
morning last at Richmond and its vicinity, in a manner that
alarmed many, and astonished every person that beheld it. From
one until three in the morning, those starry meteors seemed
to fall from every point in the heavens, in such numbers as
to resemble a shower of sky rockets..." [ref]
the Lyrids do this year? The only way to know for sure is to go
outside and look.
meteor watchers suggest the following viewing strategy: Dress
warmly. Bring a reclining chair, or spread a thick blanket over
a flat spot of ground. Lie down and look up somewhat toward the
east. Meteors can appear in any part of the sky, although their
trails will tend to point back toward the radiant--i.e., toward
Vega is a
brilliant blue-white star about three times wider than our Sun
and 25 light years away. You might have seen Vega in Carl Sagan's
movie Contact. It was the source of alien radio transmissions
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