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CHRISTMAS PROMINENCE:
So, you received a solar
telescope for Christmas? Perfect timing. A plume
of hot gas is spewing over the northeastern limb of the sun,
beckoning for attention. Take a look!
photos: from
S. Billings et al of South Portland, Maine; from
Mike Borman of Evansville, Indiana; from
Francisco A. Rodriguez of Gran Canaria, Canary Islands; from
James Screech of Bedford, England; from
Peter Desypris of Athens, Greece; from
Stephen Ames of Hodgenville, Kentucky;
EDGE-ON FOR THE HOLIDAYS:
You look through the telescope. Blink. Shake
your head and look again. The planet you expected to see in the
eyepiece is not the one that's actually there. Too much eggnog?
No, it's just Saturn's crazy Christmas tilt:
Amateur astronomer Paulo
Casquinha took the picture last night from his backyard observatory
in Quinta do Anjo, Portugal. It shows how Saturn's rings are almost
edge-on to Earth this holiday season. Viewed from the side, the
normally wide and bright rings have become a shadowy line bisecting
Saturn's two hemispheres--a scene of rare beauty.
"Everyone should take
a look before the rings begin to open up again at the end of
the month," says Casquinha. A nice bonus: When the rings are
thin, Saturn's moons become easier to see. "Note the small
spot above the rings on the right; that's Rhea."
more images: from
Masa Nakamura of Otawara, Tochigi, Japan; from
Koshu Endo of Tokyo Japan (note: Endo's video shows an Earth-orbiting
satellite zipping by Saturn)
NACREOUS CLOUDS:
In the stratosphere above Scandinavia, the winter air temperature
has dropped below -85 C. That's a magic value. At such temperatures,
tiny crystals of ice begin to form in the desert-dry air 9 to 16
miles high. And when that happens, voilà--nacreous
clouds:
"This one appeared after sunset on Christmas Eve," says
Tor Aslesen of Oslo, Norway, who snapped the picture using his Nikon
D50. "It was almost florescent, the way it stood out against
the darker twilight sky."
Nacreous clouds are a polar phenomenon. They get their intense
colors from sunlight striking ice crystals ~10 microns in diameter.
Diffraction
produces iridescence, a
phenomenon familiar to daytime sky watchers around the world.
Unlike the relatively pale iridescent clouds of mid-latitudes, however,
polar nacreous clouds are blow-your-Christmas-socks-off bright.
Northern winter is just beginning and the polar stratosphere will
grow even icier in the weeks ahead. Sky watchers in cold places
like Scandinavia, Iceland and Alaska should be alert for nacreous
colors; the best time to look is during the twilight hours after
sunset or before sunrise.
Dec.
2008 Nacreous Cloud Gallery
[January 2008 Gallery]
[Nacreous
tutorial]
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