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AURORA
WATCH: NOAA forecasters estimate
a 25% chance of polar geomagnetic storms today in
response to a medium-speed (~450 km/s) solar wind
stream, which is buffeting Earth's magnetic field.
Arctic sky watchers should be alert for Northern
Lights. Aurora alerts:
text,
voice.
THE
FIREBALLS OF FEBRUARY: A number
of unusual fireballs observed around the USA this
month have researchers wondering if Earth is passing
through a special "February swarm" of
meteoroids. [full
story]
CRESCENT
MOON ALERT: When the sun goes down
tonight, step outside and look west into the sunset.
An exquisitely, almost invisibly slender crescent
Moon is beaming through the twilight. Jens Hackmann
took this picture yesterday from Weikersheim, Germany:
"It was a lucky shot," says
Hackmann, "because many planes were criss-crossing
the sky, but not one of them got in the way of the
Moon."
Seeing such a slender Moon is difficult,
but it will become easier in the nights ahead as
the waxing crescent ascends the evening sky for
a dazzling close encounter with Venus and Jupiter.
The best nights to look are Feb. 25th and 26th.
Get the full
story and a video
from Science@NASA.
more images: from
Stefano De Rosa of Turin (Italy); from
Mark Williams of Geneva, Switzerland; from
Carl Bernhardt of Riverside, California; from
Sam Linse of Mukilteo, Washington; from
Elviro Inama of Verona, Italy
SOLAR
ECLIPSE: On Feb. 21st, the new
Moon passed in front of the sun, off-center, producing
a partial solar eclipse. The only place to see it
was from space. NASA's Solar Dynamics Observatory
(SDO) sends this picture from geosynchronous orbit
approximately 36,000 km above Earth's surface:
Using a bank of 16 megapixel cameras,
SDO observed the event at multiple extreme ultraviolet
wavelengths. Scan the edge of the Moon in this 171
Å image. The little bumps and irregularities
you see are lunar mountains backlit by solar plasma.
Also, Steele Hill, SDO's Media Specialist at the
Goddard Space Flight Center, has prepared a
movie of the event.
Beyond the novelty of observing an
eclipse from space, these images have practical
value to the SDO science team. The sharp edge of
the lunar limb helps researchers measure the in-orbit
characteristics of the telescope--e.g., how light
diffracts around the telescope's optics and filter
support grids. Once these are calibrated, it is
possible to correct SDO data for instrumental effects
and sharpen the images even more than before.
During the eclipse, the edge of the
Moon briefly covered sunspot AR1422, a source of
strong ultraviolet emissions. SDO's EVE sensor,
which measures the sun's extreme UV output, saw
a sharp drop at several wavelengths when the sunspot
was behind the Moon:
This should allow scientists to calibrate
the spectrum of energy emitted by the sunspot's
magnetic canopy--a rare opportunity, indeed.
The next solar eclipse
visible from Earth's surface occurs on May 20, 2012:
video.
February
2012 Aurora Gallery
[previous Februaries: 2011,
2010,
2009,
2008,
2007, 2006,
2004, 2003,
2002]
