|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.
Right: A Perseid fireball photographed in 1997 by Rick Scott and Joe Orman.
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
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
||"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 its
closest approach to Earth in some 60,000 years.
Above: Using an 8-inch telescope and a digital camera, Ron Wayman of Tampa, FL, took this
picture of a close encounter between the Moon and Mars on July 17, 2003.
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.
Below: The northeastern sky at 4 o'clock in the morning on August 13, 2003. Meteors will seem
to flow from a point in Perseus called "the radiant" (red dot). Don't forget to look for Saturn
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
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.
Credits & Contacts
Author: Dr. Tony Phillips
Responsible NASA official: Ron Koczor Production Editor: Dr. Tony Phillips
Curator: Bryan Walls
Media Relations: Steve Roy
The Science Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web
sites. The mission of Science@NASA is to help the public understand how exciting NASA research
is and to help NASA scientists fulfill their outreach responsibilities.