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ASTEROID NEAR MISS:
On Nov. 6th at 2132 UT, asteroid 2009
VA barely missed Earth when it flew just 14,000 km above
the planet's surface. That's well inside the "Clarke
Belt" of geosynchronous satellites. If it had hit,
the ~6-meter wide space rock would have disintegrated in the
atmosphere as a spectacular fireball, causing no significant
damage to the ground. 2009 VA was discovered just 15 hours
before closest approach by astronomers working at the Catalina
Sky Survey.
MAGNETIC FILAMENT:
Today, amateur astronomers are monitoring
a picturesque magnetic filament looping around the western
limb of the sun. Jan Timmermans sends this picture from his
backyard observatory in Valkenswaard, The Netherlands:
The portion of the filament seen in front of
the sun looks dark, because it is cooler than the inferno
below. But note how the filament glows in projection against
the black space beyond the limb. The glow comes from plasma
trapped inside the filament--not as bright as the surface
of the sun, but definitely brighter than the void.
"The image clearly shows that the only
difference between a 'dark' filament and a 'bright' prominence
is where they are located: inside or outside the solar disk,"
notes Timmermans. (diagram)
more images: from
Alan Friedman of Buffalo, New York; from
Stephen Ames of Hodgenville, Kentucky;
COMPLETE FOGBOW:
On Oct. 24th, Mila
Zinkova of San Francisco took an early morning stroll
along the beach. As her shadow stretched across the damp sand,
a ghostly white ring surrounded the dark form. "It was
a 360o fogbow--a very special sight," she
says.
Fogbows are close cousins of rainbows. The difference is
droplet size. Rainbows appear when sunlight
bounces in and out of large raindrops. The same type of
reflection produces
a fogbow, except fog droplets are much smaller. Small
droplets don't separate the colors of sunlight as widely as
large raindrops do. In a fogbow, therefore, the colors are
smeared together, producing a ghostly-white arc.
"Nearby I saw a
spiderweb," adds Zinkova. "The whole web was
covered with tiny fog droplets, the droplets that made fogbow
possible."
Only one question remains: Why is the fogbow a complete circle?
Most fogbows, like rainbows, display only their upper half.
Atmospheric optics expert Les Cowley has the answer: "All
fogbows would like to be a full circle centered on your shadow,
but usually there are insufficient tiny fog droplets near
the ground to make a bow bright enough to see. Here the dark
background helps to reveal it. "
October
Northern Lights Gallery
[previous Octobers: 2008,
2007, 2006,
2004, 2003,
2002, 2001]
Explore
the Sunspot Cycle |
