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LUNAR IMPACT VIEWER'S
GUIDE: On Friday morning, Oct. 9th, you
can watch a pair of spacecraft crash into the Moon with your own
eyes. The purposeful impacts are the climax of NASA's LCROSS mission
to unearth signs of water in lunar soil. Today's
story from Science@NASA tells how and where to look.
FINDING GROUND ZERO:
If you plan to watch this Friday's
lunar impact through a backyard telescope, start practicing
now. Pinpointing Cabeus among so many other craters around the lunar
south pole isn't easy. David Evans of Coleshill, UK, found the impact
site on Oct. 3rd using his Meade 8-inch
telescope:
Click
to view a larger image
One way to know you've found the right crater: It'll
be the one with an fluffy plume on Friday morning. Mission scientists
expect debris from the double-impact of LCROSS and its booster rocket
to rise about 7 kilometers over the rim of Cabeus. There will be
two plumes, one from the booster rocket (4:30 am PDT) and another
from the LCROSS mothership (4:34 am PDT). Each is expected to linger
in sunlight for 60 to 90 seconds before falling back into the shadowy
depths of Cabeus. The surface brightness of the plumes should be
similar to that of surrounding sunlit terrain.
More Lunar Impact Resources:
ITALIAN GLORY: Yesterday,
photographers Andrea Alessandrini and Paolo Candy were flying over
Italy's Tirrenum Sea when they looked out the window of their airplane
and saw this:
It was a
glory--"one of the prettiest I've ever seen," says
Candy. And that means something because he's written a
book on the subject.
Glories are rings of light around your shadow. They
are caused by sunlight reflected backwards from water droplets in
clouds. Exactly how backscattering produces the colorful rings is
a mystery
involving surface waves and multiple reflections within individual
droplets. Each sighting is a puzzle--all the more reason to seek
them out.
"Glories are often seen from aircraft,"
notes atmospheric optics expert Les Cowley. "Get a seat opposite
the sun and watch them ring the aircraft's shadow." Airplanes
are not absolutely required, however. All you really need is a high
perch and moist clouds. Look for glories on mountains
and hillsides, in sea
fog, and even indoors.
Sept.
2009 Aurora Gallery
[previous Septembers: 2008,
2007,
2006, 2005,
2004, 2002,
2001]
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