Where's Saturn? Is that a UFO--or the ISS? What's the name of that
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fun new astronomy helper from Meade. HAPPY
SOLSTICE: This morning, Dec. 22nd at 6:08
am UT, the sun reached its lowest declination of the year: -23.5
degrees. Astronomers call this the winter
solstice; it marks the first day of winter and the longest night
of the year in the northern hemisphere. In the southern hemisphere,
where things are reversed, it marks the beginning of summer and
the longest day. Either way, happy solstice!
URSID METEORS:
Comet 8P/Tuttle is coming and it is bringing a meteor shower with
it. "We could be in for a Merry surprise on Dec. 22nd when
Earth passes through a trail of comet dust," says astronomer
Peter Jenniskens of the SETI Institute. Previous returns of Comet
Tuttle to the inner solar system have been attended by outbursts
of meteors, most recently in 1980 and 1994. During those flurries,
dozens of meteors per hour flowed from the constellation Ursa Minor--hence
the name of the shower, "the Ursids."
Above: Comet
8P/Tuttle photographed Dec. 21st by Mike
Holloway of Van Buren, Arkansas. [sky
map] [ephemeris]
[orbit]
[more]
Although Ursids have a reputation for being faint, "we are
not certain about this," says Jenniskens. "Because winter
weather keeps many observers indoors, Ursid outbursts have never
been widely observed and they may contain a fair number of bright
meteors. We have a lot to learn." That's why he hopes sky watchers
will keep an eye on the northern sky this weekend; Ursid meteors
emerge not far from the north star, Polaris. According to models
by Jenniskens and colleagues, the peak will occur between 2100 and
2200 UT (4-5 pm EST) on Dec. 22nd with meteors visible as much as
four hours before and after that time. Anything could happen, from
a dud to a blast. Bundle up and
look!
MOILANEN ARC:
Sky watchers in Oslo, Norway, will always remember Dec. 16, 2007:
It was the "Day of the Ice Halo." Diamond
dust ice crystals drifting through the air caught the rays of
the sun and transformed ordinary sunbeams into a dazzling array
of luminous arcs, V's, and pillars--collectively known as halos.
Oslo resident Steinar Midtskogen
snapped this picture using his Nikon
D70:
One of the V's in this photo turns out to be both rare and mysterious.
Atmospheric optics expert Les Cowley explains:
"The Moilanen arc, the V-shaped arc closest to the sun in
this picture, is named after its discoverer, Jarmo Moilanen of Finland.
It is a mystery. We can simulate
it mathematically using a sharp prism with faces tilted 34 degrees
to each other instead of the usual 60
degrees of ordinary ice crystals. That is the easy bit! We do
not yet know what real crystals in the sky make it. They could be
twinned crystals, two interlocking crystals, or something even more
exotic. Look out for it and, who knows, you might also discover
your own halo!"
more Oslo images: from
Johannes Froyen of Oslo, Norway; from
Anders Gjørwad Hagen near Oslo, Norway; from
Odd-Tore Saugerud near Oslo, Norway; from
Signe S. Flugsrud of Oslo, Norway;
2007
Geminid Meteor Gallery
[World
Map of Geminid Sightings]
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[meteor alerts] [Night
Sky Cameras]
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