+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
July
31, 2009: Earth
is entering a stream of dusty debris from Comet Swift-Tuttle,
the source of the annual Perseid meteor shower. Although the
shower won't peak until August 11th and 12th, the show is
already getting underway.
Brian
Emfinger of Ozark, Arkansas, photographed this early Perseid
just after midnight on Sunday, July 26th:
"I used an off-the-shelf digital camera
to capture this fireball and its smoky trail," says Emfinger.
"It was a bright one!"
Don't
get too excited, cautions Bill Cooke of NASA's Meteoroid Environment
Office. "We're just in the outskirts of the debris stream
now. If you go out at night and stare at the sky, you'll probably
only see a few Perseids per hour."
This will change, however, as August unfolds.
"Earth
passes through the densest part of the debris stream sometime
on August 12th. Then, you could see dozens of meteors per
hour."
For
sky watchers in North America, the watch begins after nightfall
on August 11th and continues until sunrise on the 12th. Veteran
observers suggest the following strategy: Unfold a blanket
on a flat patch of ground. (Note: The middle of your street
is not a good choice.) Lie down and look up. Perseids can
appear in any part of the sky, their tails all pointing back
to the shower's radiant in the constellation Perseus. Get
away from city lights if you can.
There
is one light you cannot escape on August 12th. The 55% gibbous
Moon will glare down from the constellation Aries just next
door to the shower's radiant in Perseus. The Moon is beautiful,
but don't stare at it. Bright moonlight ruins night vision
and it will wipe out any faint Perseids in that part of the
sky.
Above:
Looking northeast around midnight on August 11th-12th. The
red dot is the Perseid radiant. Although Perseid meteors can
appear in any part of the sky, all of their tails will point
back to the radiant. Image copyright: Spaceweather.com, used
with permission.
The
Moon is least troublesome during the early evening hours of
August 11th. Around 9 to 11 p.m. local time (your
local time), both Perseus and the Moon will be hanging low
in the north. This low profile reduces lunar glare while positioning
the shower's radiant for a nice display of Earthgrazers.
"Earthgrazers
are meteors that approach from the horizon and skim the atmosphere
overhead like a stone skipping across the surface of a pond,"
explains Cooke. "They are long, slow and colorful—among
the most beautiful of meteors." He notes that an hour
of watching may net only a few of these at most, but seeing
even one can make the whole night worthwhile.
The Perseids are coming. Enjoy the show.
SEND
THIS STORY TO A FRIEND
Author: Dr.
Tony Phillips | Credit: Science@NASA
|