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MT. REDOUBT ERUPTS:
After months of teasing seismic activity, Alaska's Mt.
Redoubt finally erupted on March 23rd. The blast hurled clouds
of ash into the lower stratosphere at least 18 km high. The last
time an Alaskan volcano blew its top (Kasatochi in August 2008),
stratospheric aerosols caused fantastic
sunsets
around the northern hemisphere--a phenomenon that could recur in
the days and weeks ahead. Mt. Redoubt isn't finished. "A large
explosion may occur again at anytime," says the Alaska Volcano
Observatory. Stay tuned for updates.
SATELLITE WRECKAGE:
Last month, the Iridium 33 communications
satellite was completely destroyed when it collided
with Russian satellite Cosmos 2251. Or was it? Satellite observer
Marco Langbroek has
observed a substantial piece of Iridium 33 wreckage apparently still
intact tumbling over the Netherlands:
Photo details: Canon
EOS 450D + EF 50/2.5 Macro lens
"This photo is one of two I shot on March 20th showing Iridium
33 flashing at magnitude +2 with a period of 4.6 to 4.7 seconds,"
says Langbroek. "Simone Corbellini in Italy and I have independently
observed it occasionally giving off much brighter flashes of magnitude
-2. Simone thinks that the main mission antennas are still intact
and glinting in the orbital sunlight."
"It seems that Iridium 33 received a glancing blow,"
he suggests. "Pieces scattered off, but there is still a considerable
body left."
Readers, if you would like to try to observe the wreckage, check
the Simple Satellite Tracker for flyby times.
You might see nothing when Iridium 33 passes overhead, but the possibility
of a bright flash makes it worth a try.
SOMETHING MYSTERIOUS
IN THE STATE OF DENMARK: On March 20th, Danish
photographer Jesper Gronne looked up at the clouds and saw not just
one or two but three concentric halos around the sun. Before
the rare display could fade, he grabbed his camera (a Canon
5D) and snapped more than 20 pictures. Stacking the images on
his computer yielded a pin-up quality record of the event:
"I never expected to see such a rich variety
of ice halos here in lowland Denmark--and it's not even winter anymore!"
he marveled.
What could cause such an apparition? Atmospheric optics
expert Les Cowley explains: "We can work outwards from the
sun to explore the mysteries of this display. The first ring is
an exceptionally bright and rare 9-degree
halo made by tumbling pyramidal
ice crystals in the clouds. The same crystals also produced
displays on the other side of the North Sea the night
before. The inner halo's bright upper and lower patches could
be something very rare indeed, plate arcs from aligned pyramids.
But we must be cautious, they could just be spots of thicker cloud!"
"The next bright ring is at first sight the common
22-degree halo but with so many pyramidal crystals about it could
also be a combination of other pyramidal halo rings.
There are hints too of 18 degree pyramidal halos inside it. At least
the two sundogs are familiar sights!"
"Farther from the sun at top is another familiar
halo, the ‘smile-in the-sky' circumzenithal
arc made from ordinary ice plates. But the one touching it and
curving downwards is another mystery. We know it is either
a supralateral arc or a 46 degree halo. But if a supralateral, we
would expect an upper tangent arc from the same column crystals
– there is none. If a 46 degree halo then the inner 22 degree ring
should be much brighter! Displays like this one are fascinating
and need long studies of many photos to unravel and be sure of their
secrets."
March
2009 Aurora Gallery
[previous Marches: 2008,
2007, 2006,
2005, 2004,
2003, 2002]
Comet
Lulin Photo Gallery
[Comet
Hunter Telescope: review]
[Comet
Lulin finder chart]
Explore
the Sunspot Cycle
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