Great Perseids
- From: baalke@xxxxxxxxxxxxx
- Date: Mon, 16 Jul 2007 13:44:36 -0700
http://science.nasa.gov/headlines/y2007/11jul_greatperseids.htm
Great Perseids
NASA Science News
July 11, 2007
July 11, 2007: Got a calendar? Circle this date: Sunday, August 12th.
Next to the circle write "all night" and "Meteors!" Attach the above
to
your refrigerator in plain view so you won't miss the 2007 Perseid
meteor shower.
"It's going to be a great show," says Bill Cooke of NASA's Meteoroid
Environment Office at the Marshall Space Flight Center. "The Moon is
new
on August 12th--which means no moonlight, dark skies and plenty of
meteors." How many? Cooke estimates one or two Perseids per minute at
the shower's peak.
The source of the shower is Comet Swift-Tuttle. Although the comet is
nowhere near Earth, the comet's tail does intersect Earth's orbit. We
glide through it every year in August. Tiny bits of comet dust hit
Earth's atmosphere traveling 132,000 mph. At that speed, even a
smidgen
of dust makes a vivid streak of light--a meteor--when it
disintegrates.
Because Swift-Tuttle's meteors fly out of the constellation Perseus,
they are called "Perseids."
Note: In the narrative that follows, all times are local. For
instance,
9:00 pm means 9:00 pm in your time zone, where you live.
The show begins between 9:00 and 10:00 pm on Sunday, August 12th, when
Perseus rises in the northeast. This is the time to look for Perseid
Earthgrazers--meteors that approach from the horizon and skim the
atmosphere overhead like a stone skipping the surface of a pond.
"Earthgrazers are long, slow and colorful; they are among the most
beautiful of meteors," says Cooke. He cautions that an hour of
watching
may net only a few of these--"at most"--but seeing even one makes the
long night worthwhile.
As the night unfolds, Perseus climbs higher and the meteor rate will
increase many-fold. "By 2 am on Monday morning, August 13th, dozens of
Perseids may be flitting across the sky every hour." The crescendo
comes
before dawn when rates could exceed a meteor a minute.
For maximum effect, Cooke advises, "get away from city lights." The
brightest Perseids can be seen from cities, he allows, but the greater
flurry of faint, delicate meteors is visible only from the
countryside.
Scouts, this is a good time to go camping.
And there's a bonus: Mars. In the constellation Taurus, just below
Perseus, Mars shines like a bright red star. Many of the Perseids you
see on August 12th and 13th will flit right past it. Instead of
following the meteor, you may find you have a hard time taking your
eyes
off Mars. There's something bewitching about it, maybe the red color
or
perhaps the fact that it doesn't twinkle like a true star. You stare
at
Mars and it stares right back.
Earth and Mars are converging for a close encounter in December 2007.
NASA is taking advantage by launching a new mission to Mars--the
Phoenix
Lander
Phoenix will touch down on an arctic plain where it can dig into the
ground and investigate layers of soil and ice, searching for, among
other things, a habitable zone for primitive microbes. The launch
window
opens on August 3rd, so by the time the Perseids arrive Phoenix may be
hurtling toward the Red Planet. Landing: late Spring 2008.
It's something to think about at four in the morning, with Mars rising
in the east, meteors flitting across the sky, and a summer breeze
rustling the legs of your pajamas.
Maybe you should go circle your calendar again.
.
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