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MAJOR
X-FLARE + CME UPDATE: Earth-orbiting
satellites have detected a long-duration X1.4-class
solar flare coming from a new sunspot on the sun's
eastern limb. The blast, which peaked at 1100 UT,
produced a significant coronal mass ejection (CME).
Using data from the SOHO-STEREO fleet of spacecraft,
analysts at the Goddard Space Weather Lab have modeled
the trajectory of the CME and concluded that the
body of the cloud will not hit Earth. A minor glancing
encounter with the outskirts of the CME is, however,
possible on Sept. 25th. [CME: movie,
forecast
track]
AURORAS
UNDERFOOT: Solar activity is picking
up, and no one has a better view of its effect on
Earth than the crew of the International Space Station.
During a geomagnetic storm on Sept. 17th, astronauts
recorded a must-see movie of auroras dancing underfoot:
Taken over the southern Indian Ocean,
the movie spans a 23-min period from 17:22:27 to
17:45:12 GMT on Sept. 17.
Note how the underbelly of the space
station glows green from the reflected light of
the auroras below. Also, in the distance, Sirius
the dog star and Orion the Hunter can be seen rising
feet-first into the night sky.
The storm, which registered a moderate
6 on the 0-to-9 K-index
scale of geomagnetic disturbances, was caused by
a coronal mass ejection (CME) hitting Earth's magnetic
field. It was just a glancing blow, but with CMEs
that is often enough to spark bright auroras over
both ends of Earth. The space station was flying
over the southern hemisphere at the time of the
display. Observers in the northern hemisphere saw
it
too.
A similar storm could be in the offing
this week. Another CME is heading toward Earth,
and it appears likely to deliver a glancing blow
on Sept. 22nd around 23:00 UT. Sky watchers above
and below should be alert for auroras.
Aurora alerts: text,
voice.
September
2011 Aurora Gallery
[previous Septembers: 2010,
2009, 2008,
2007,
2006,
2005,
2004]
RE-ENTRY
ALERT: NASA's UARS satellite is
making its final orbits around Earth, tumbling and
flashing brightly as it descends toward a Sept.
23rd re-entry. Amateur astronomer Jim Saueressig
II caught the bus-sized satellite flying over Burlington,
Kansas, on Sept. 20th (image).
"It was easily visible in spite of the moonlight
and the twilight of the sunrise. The tumble and
associated flares were very apparent," he says.
Satellite tracking expert Ted Molczan
has used USSTRATCOM's orbital elements of UARS to
predict a decay time "late on Sep 23, roughly
between 18:00 and 22:00 UTC." Click on the
map to view ground tracks corresponding to this
interval:
"There is still potential for
the estimated time of decay to shift somewhat before
it begins to narrow down," cautions Molczan.
The disintegration of UARS is expected
to produce a fireball that could be visible even
in broad daylight. Not all of the spacecraft will
burn up in the atmosphere, however; according to
a NASA risk
assessment, as many as 26 potentially hazardous
pieces of debris could be scattered along a ground
track some 500 miles long. The same report puts
the odds of a human casualty at 1 in 3200.
For last-chance sightings of this
brightly flashing satellite, please check the Simple
Satellite Tracker or download the Satellite
Flybys app for your smartphone.
more images: from
Theirry Legault of Dunkerque, France; from
Oscar MartÃn Mesonero of Madrid, Spain;
