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ORIONID
METEOR UPDATE: Earth is passing
through a broad stream of debris from Halley's Comet,
source of the annual Orionid
meteor shower. Unlike the displays of previous
years, however, the Orionids of 2012 have not put
on a very good show. Sky watchers have seen, at
most, one to two dozen meteors per hour during the
peak activity of Oct. 21-22. The shower may be weak,
but it's not over yet. Enthusiasts should remain
alert for fast, faint pieces of Halley's Comet in
the pre-dawn sky on Monday and Tuesday. [gallery]
[meteor radar] [reports]
ACTIVE
SUNSPOT : New sunspot AR1598 is
crackling with C-
and M-class solar flares. One of the explosions,
an M9-flare on Oct. 20th, produced a bright flash
of extreme UV radiation recorded by NASA's Solar
Dynamics Observatory:
Radiation from the flare sent a wave
of ionization rippling through Earth's upper
atmosphere, temporarily disturbing the transmission
of low-frequency radio signals around Europe and
North America. The sunspot has also produced at
least one bright CME (movie),
but Earth was not in the line of fire.
More flares are in the offing. NOAA
forecasters estimate a 60% chance of M-flares and
a 5% chance of X-flares during the next 24 hours.
Solar flare alerts:
text,
voice.
METEOR
MAKES LANDFALL: A small asteroid
that exploded over the San Francisco Bay Area on
Oct. 17th, shaking houses with its sonic boom, might
have scattered pieces of itself on the ground. That's
the conclusion of Peter Jenniskens of the NASA Ames
Research Center. He triangulated data from a pair
of meteor surveillance
cameras to determine the fireball's trajectory,
denoted by the black arrow in the map below:
"The asteroid entered at a [relatively
slow] speed of 14 km/s. There's a good chance that
a fairly large fraction of this rock survived and
fell somewhere around the North Bay," says
Jenniskens. "Much more accurate results will
follow from a comprehensive study of the video records.
Now, we hope that someone recovers a meteorite on
the ground."
In the map, red dots represent the
surveillance cameras Jenniskens used to calculate
the trajectory. The black arrow traces the asteroid's
path; 85 km and 39 km are the altitudes of the asteroid
at the two ends of the arrow. Jenniskens adds that
"39 km is not the end point, but the final
bit captured by the San Mateo video camera."
The disintegrating asteroid continued beyond the
tip of the arrow for a possible landfall somewhere
north of San Francisco. Stay tuned for updates
on the meteorite hunt.
Note: This was not
an Orionid.
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Noctilucent Cloud Photo Gallery
[previous years: 2003,
2004,
2005,
2006,
2007,
2008,
2009,
2011]
