ASTRONOMY
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BIG INTERSTELLAR DISCOVERY:
The solar system is passing through an interstellar cloud
that physics says should not exist. In the Dec. 24th issue
of Nature, a team of scientists reveal how NASA's
Voyager spacecraft have solved the mystery. Get the full
story from Science@NASA.
AURORAS AND A RAINBOW
AT NIGHT: At midnight on Dec. 23rd, Karl Johnston
found himself climbing down a cliff on the banks of the Slave
River, near Fort Smith in the Northwest Territories of Canada.
He paused for breath, looked out over the rapids, and this
is what he saw:
"A rainbow was cutting through the aurora
borealis," he says.
A rainbow at night? "Moonlight
was shining into the mist above the rapids--and that's what
made the rainbow," he explains. Technically, it's called
a fogbow. Fogbows
are close
cousins of rainbows and they are formed
in essentially the same way: light bounces in and out of water
droplets to produce a luminous arc.
Johnston's lunar fogbow formed above the rapids
just as a solar wind stream was buffeting Earth's magnetic
field, giving rise to auroras and a rare conjunction of Arctic
night lights. It's enough to make you scale a cliff at midnight.
More images: #1,
#2,
#3.
UPDATED:
December Northern Lights
Gallery
[previous Decembers: 2008,
2007, 2006,
2005, 2001,
2000]
RINGED PLANET:
Saturn isn't the only planet with rings. Earth has one, too,
a ring of geostationary satellites. Click on this image and
cross your eyes to see it pop out of the screen in 3D:
Science teacher Tom
Wagner of Waterloo, Iowa, created the image on Christmas
Eve using Makoto Kamada's 3D
satellite viewing program. "Earth looks a bit like
a Christmas ornament hanging suspended in the middle of the
satellite swarm."
Geostationary satellites orbit 36,000 kilometers
above Earth's surface. They go around our planet once every
24 hours, which means they hang over a fixed point on the
ground--perfect for monitoring weather, beaming down TV signals,
and relaying telecommunications. The ring is sometimes called
the "Clarke
Belt" after Arthur C Clarke who popularized the idea
of geostationary satellites in the mid-1940s, more than a
decade before the Space Age began.
In addition to the Clarke Belt, Wagner's image
also shows hundreds of low-Earth orbit satellites hugging
the planet only a few hundred kilometers high, and many satellites
at intermediate altitude. Space is a busy place. You can see
how busy by viewing more of Wagner's 3D-sat images
here.
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