[Vision2020] Meteors to Light Up Night Skies
thansen at moscow.com
Wed Aug 11 05:43:31 PDT 2004
Greetings Visionaires -
>From today's (August 11, 2004) Spokesman Review.
Meteors to Light Up Night Skies
Perseid shower one of year's most reliable astronomical events
August 11, 2004
Find your way to a patch of dark sky tonight and you are likely to be
delighted by one of the year's most reliable astronomical events.
Earth is encountering the annual Perseid meteor shower, a celestial
bombardment of shooting stars and fireballs caused by tiny bits of comet
dust being burned as they enter the atmosphere.
Earth's orbit around the sun takes it through the debris left by the comet
Swift-Tuttle each year at this time, but the peak of the show arrives on
Aug. 11 or 12.
This year's peak is forecast to occur at 4 a.m. on Thursday, but viewing
earlier in the night should be good as well, said Zeke Zechmeir, president
of the Spokane Astronomical Society.
Skywatchers can expect clear skies and mild temperatures, according to the
National Weather Service forecast, and a waning moon won't rise until around
2:30 a.m., ensuring darkness for optimum viewing.
"The Perseids are always a good performer. They are always worth watching,"
He recommended getting away from bright city lights and busy commercial
areas where the night sky is obscured by glare. Also, choose a place that
has an open view of the sky, especially to the northeast.
According to Sky and Telescope Magazine, the Perseid meteor shower is one of
the two most dependable meteor showers each year. The Geminid shower in
December is the other.
The August event takes its name from the constellation Perseus, which
provides the focal point for the shower. The meteors will appear to be
coming from an area of the sky next to the constellation. This is known in
astronomy as the radiant of the shower.
As with most meteor showers, the best viewing comes after midnight when the
radiant rises higher into the sky and Earth's rotation points viewers into
the direction of the planet's orbit through the comet dust.
Perseus and its neighboring constellation Cassiopeia can be found in the
northeast sky. Early in the evening, the radiant is low - but as the radiant
rises, the number of meteors could increase to as many as 50 to 60 per hour.
Experienced skywatchers know that the radiant becomes apparent after
watching for any length of time.
Zechmeir said there is a chance this year's showers will be more active than
during other years because Jupiter's gravitational pull is allowing Earth to
pass closer to the center of the comet trail.
The comet dust is dispersed enough that the showers can be seen off and on
between July 17 and Aug. 24, he said.
Sky and Telescope Magazine said the meteoroids in the Perseid stream range
in size from pebbles to sand grains. They have a consistency like bits of
ash. They ram into our upper atmosphere at a speed of 60 kilometers per
hour, creating incandescent trails of light from ionized air.
The best of the meteors look like fireballs and are apparent even if they
strike the atmosphere during late dusk or early dawn. The predawn sky is
also being graced by Venus in the east.
In addition to this week's meteor shower, Zechmeir said, an unusually active
sun spot could trigger appearances of the northern lights, or aurora
borealis, later this week.
Auroras have been reported periodically in the past several weeks as far
south as southern Oregon, he said. Some of the best auroras occurred when
the current sun spot was pointed toward Earth in July. The sun's rotation
has caused the spot to be facing Earth again this week. Since the moon will
be in its crescent phase, viewing of any possible auroras should be good.
We could learn a lot from crayons: some are sharp, some are pretty, some are
dull, some have weird names, and all are different colors....but they all
exist very nicely in the same box.
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