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QUIET
SUN : Solar activity is low with
only a slight (15%) chance of M-class solar flares
during the next 24 hours. Solar
flare alerts: text,
voice.
BIG
SUN-DIVING COMET DISCOVERED: Astronomy
forums are buzzing with speculation about newly-discovered
Comet C/2012 S1 (ISON). Currently located
beyond the orbit of Jupiter, Comet ISON is heading
for a very close encounter with the sun
next year. In Nov. 2013, it will pass less than
0.012 AU (1.8 million km) from the solar surface.
The fierce heating it experiences then could turn
the comet into a bright naked-eye object. (continued
below)
Comet ISON photographed by E. Guido,
G. Sostero & N. Howes on Sept. 24. [more]
Much about this comet--and its ultimate
fate--remains unknown. "At this stage we're
just throwing darts at the board," says Karl
Battams of the NASA-supported Sungrazer
Comet Project, who lays out two possibilities:
"In the best case, the comet
is big, bright, and skirts the sun next November.
It would be extremely bright -- negative magnitudes
maybe -- and naked-eye visible for observers in
the Northern Hemisphere for at least a couple of
months."
"Alternately, comets can and
often do fizzle out! Comet
Elenin springs to mind as a recent example,
but there are more famous examples of comets that
got the astronomy community seriously worked up,
only to fizzle. This is quite possibly a 'new' comet
coming in from the Oort
cloud, meaning this could be its first-ever
encounter with the Sun. If so, with all those icy
volatiles
intact and never having been truly stressed (thermally
and gravitationally), the comet could well disrupt
and dissipate weeks or months before reaching the
sun."
"Either of the above scenarios
is possible, as is anything in between," Battams
says. "There's no doubt that Comet ISON will
be closely watched. Because the comet is so far
away, however, our knowledge probably won't develop
much for at least a few more months."
Meanwhile, noted comet researcher
John Bortle has pointed
out a curious similarity between the orbit
of Comet ISON and that of the Great Comet of 1680.
"Purely as speculation," he says, "perhaps
the two bodies could have been one a few revolutions
ago."
Stay tuned for updates.
Realtime
Space Weather Photo Gallery
AUTUMN
LIGHTS: The onset of northern autumn
means it's aurora
season. For reasons researchers don't fully
understand, equinoxes are the best times to see
Northern Lights. And, right on cue, the Arctic Circle
is glowing. Marianne Bergli sends this picture of
auroras shimmering directly above Storfjord, Norway:
"Last night it was difficult
to select [which part of the sky to photograph].
The auroras were dancing everywhere," says
Bergli. "Eventually I was just lying on my
back looking up. It was absolutely, unbelievable
wonderful."
As the week begins, the solar wind
velocity is low (~350 km/s), but at this time of
year it only takes a gentle gust to ignite bright
auroras around the Arctic Circle. High-latitude
sky watchers should remain alert for auroras.
Aurora alerts: text,
voice.
Realtime
Aurora Photo Gallery
Realtime
Noctilucent Cloud Photo Gallery
[previous years: 2003,
2004,
2005,
2006,
2007,
2008,
2009,
2011]
