The 2003 Perseid Meteor Shower

http://science.nasa.gov/headlines/y2...rseids2003.htm

The 2003 Perseid Meteor Shower
NASA Science News
July 17, 2003

Mark these dates on your calendar: August 12th and 13th.


It's time to get ready for the Perseid meteor shower.

The Perseids are probably the best-watched of any annual meteor shower.
They come in mid-August when it's warm and comfortable to be outside at 4
o'clock in the morning. They are bright, numerous, and dependable.

This year the shower peaks on Wednesday, August 13th.

When skies are dark and clear, observers often see as many as one hundred
Perseids per hour--an impressive display. This year, however, skies won't
be dark. A glaring full moon will wipe out many faint meteors and reduce
by a factor of two or three the number you can see.

Even so, it's worth planning a trip to the country or rearranging your
camping schedule to be outdoors when the Perseids arrive.

"No matter where you live, the best time to look
will be just before dawn on Wednesday morning,
August 13th," says Bill Cooke of NASA's Space
Environments Team at the Marshall Space Flight
Center. At that time, the sky overhead will be
tilted into the debris stream of Comet
Swift-Tuttle--the source of the Perseid meteors.
Furthermore, the moon will be low in the sky before dawn. You can stand
in the shadow of a building or a hill or some other Moon-baffle to reduce
its glare.

Last year in November Cooke led a team of astronomers to study the Leonid
meteor storm, which likewise happened during a full moon. "Observers who
ducked into the shadows counted twice as many meteors as those who stood
in full moonlight."

Another way to minimize the bad effects of the moon is to travel to a
site where the air is clear.

Even when you face away from the Moon, Cooke explains, the air glows
because of moonlight scattered from air molecules and aerosols (e.g.,
water droplets, dust and pollution). This glow will be less in places
where the air is dry and pollution-free. Mountaintops are excellent
because they rise above the humid lower atmosphere and most aerosols.

Once you find your observing site and settle in--a comfortable chair and
blankets are recommended--there's no special direction you have to face.
Perseids can appear anywhere in the sky.

"But don't look toward the Moon," Cooke cautions. "That will ruin
your night vision."

Actually, go ahead and look at it just once, because on August 13th the
Moon and Mars will be pleasingly close together, only a few Moon-widths
apart. Other than the Moon itself, Mars will be the brightest object in
the sky that night--red, piercing, and a joy to see through a telescope.
When the Perseid meteor shower peaks, Mars will be only two weeks away
from it's closest approach to Earth in some 60,000 years.

When you see a Perseid, perhaps even one streaking past Mars, trace its
tail backward. It will lead to the constellation Perseus.

"Perseid meteors stream out of a point in Perseus called the radiant," he
explains. Because of foreshortening, meteors near the radiant appear
short and stubby. Meteors away from the radiant are longer and more
eye-catching.

Speaking of long meteors... You can see some really long ones on Tuesday
evening, August 12th. They're called Earthgrazers. Earthgrazers are
shooting stars that emerge from the horizon and streak horizontally
through the atmosphere. They tend to be slow, bright and colorful.

Between 8 p.m. and 9:30 p.m. on August 12th is a good time to look for
Perseid Earthgrazers because," explains Cooke, "the constellation Perseus
will be hanging low near the northeastern horizon--a good geometry for
grazing meteors."

The Moon will be hanging low then, too, so once again it should be
possible to find some moon shadows where the glare is less.

"Earthgrazers are somewhat rare," notes Cooke. "You won't see many of
them, but they're very pretty."

Earthgrazing meteors. The Moon and Mars. The dependable Perseids. It all
happens on August 12th and 13th. Mark your calendar and don't miss the
show.