[meteorite-list] Perseid Earthgrazers

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Aug 8 12:08:22 2006
Message-ID: <200608081557.IAA00572_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/headlines/y2006/07aug_perseids.htm

Perseid Earthgrazers
NASA Science News
August 7, 2006

August 7, 2006: Blame it on the Moon: The 2006 Perseid meteor shower is
going to be a dud. Oh, Earth will pass through the Perseid meteoroid
stream, as usual. And meteors will flit across the sky. But when the
shower peaks on Saturday morning, August 12th, the glare of the 87%-full
Moon will overwhelm most Perseids, making them impossible to see.

You might see some Perseids, after all. The trick is to look before the
Moon rises. Plan your meteor watch for 8:30 p.m. to 10 p.m. on Friday,
August 11. The Moon won't be up yet and, in the darkness just after
sunset, a special kind of meteor may appear: the Perseid Earthgrazer.

Earthgrazers are meteors that skim the top of Earth's atmosphere like a
stone skipping across the surface of a pond. They appear when the
radiant of a meteor shower is near the horizon, spewing meteoroids not
down, but horizontally overhead. Such will be the case on Friday evening
after sunset when Perseus (the radiant of the Perseids) first peeks over
the northern horizon.

Don't expect a storm. Earthgrazers are rare. An hour's watching might
net no more than one or two, but that's plenty. Earthgrazers are
colorful and gracefully slow. People who see one talk about it for years.

Looking for Earthgrazers is simple: Spread a blanket on the ground, lie
down and look up. A reclining lawn chair facing north works just as
well. Perseid Earthgrazers streak overhead, flying generally north to south.

If you haven't spotted an Earthgrazer by 10 p.m., you probably won't. By
10 p.m., Perseus will have risen too high in the sky for grazing
meteoroids. (Try skipping a stone by throwing it down into a pond and
you'll see the problem.) Plus, the Moon itself rises around 10 p.m. to
put a real damper on things.

The rest of the night is for contrarians, people who stay up until dawn
in spite of the moonlight. They'll see some Perseids, a small fraction
of the norm, to be sure, but not zero. Occasionally, a really bright
fireball might streak across the sky, making the long night worthwhile.
It pays to resist!

Next year will be better. The 2007 Perseids peak with no Moon in sight.
Until then, watch out for Earthgrazers.
Received on Tue 08 Aug 2006 11:57:50 AM PDT