When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.
The Canadian Meteor Orbit Radar (CMOR)
detected an outburst of Andromedid meteors on Dec.
8th. "Meteor rates were near 20 per hour (ZHR),"
reports Bill Cooke of NASA's Meteoroid Environment
Office. "The shower could increase in intensity
on Dec. 9th, so we hope observers will be alert
for meteors." Andromedid meteoroids come from
Biela, which broke apart in the 19th century.
The shower's radiant in Cassiopeia is high in the
sky after sunset for observers in the Northern Hemisphere.
A similar outburst of Andromedids in 2011 was rich
in faint meteors. If the 2013 outburst is the same,
dark skies will be required to see it.
AURORAS AND METEORS:
A fast stream of solar wind is buffeting Earth's
magnetic field. When the stream arrived during the
late hours of Dec. 7th, a G2-class
geomagnetic storm broke out around the poles and
Northern Lights spilled over the Canadian border
into several US states. Patrick Daigle sends this
photo from Cameron, Montana:
"Just before bedtime I checked
Spaceweather.com. That made me change my plans,"
says Daigle. "Instead of going to bed, I went
out into the cold (-24 F) in search of Northern
Lights. While I was snapping pictures, I noticed
well over a dozen shooting stars. I believe the
one pictured above is an Andromedid."
NOAA forecasters estimate a 40% chance
of additional geomagnetic storms on Dec. 9th. High-latitude
sky watchers should remain alert for auroras as
the solar wind continues to blow.
Aurora Photo Gallery
THE GHOST OF COMET
ISON: On Friday, Dec. 6th, leading
researchers from NASA's Comet ISON Observing Campaign
(CIOC) held an informal workshop at the Johns Hopkins
Applied Physics Lab. One of the key questions they
discussed was, Did Comet ISON survive?
It might seem surprising that anyone is still asking.
After all, the "comet" that emerged from
the sun's atmosphere on Thanksgiving day appeared
to be little more than a disintegrating cloud of
dust. This movie from the STEREO-A spacecraft (processed
by Alan Watson) shows the V-shaped cloud fading
into invisibility on Dec. 1st:
The answer hinges on the contents
of that cloud. Is it nothing more than a cloud of
dust--or could there be some some fragments of the
disintegrated nucleus still intact and potentially
A key result announced at the workshop
comes from SOHO, the Solar and Heliospheric Observatory.
According to the spacecraft's SWAN instrument, the
comet stopped producing so-called Lyman alpha photons
soon after its closest approach to the sun. Karl
Battams of the CIOC explains what this means: "Without
getting technical, Lyman-Alpha is a consequence
of sunlight interacting with hydrogen, and if we
are not seeing that interaction then it means that
the levels of hydrogen (and hence ice) are extremely
low. This is indicative of a completely
burned out nucleus, or no nucleus at all."
"The evidence appears strong that at some
point approaching perihelion - whether days or hours
- Comet ISON likely began to completely fall apart,"
he continues. "What remains of ISON now is
going to be either just a cloud of dust, or perhaps
a few very depleted chunks of nucleus. Either way,
it's not going to flare up at this point and we
should assume the comet's show is over."
"However, we do need to verify this,"
says Battams. "Hopefully the Hubble team can
come to the rescue! In mid-December, Hubble will
be pointed in the direction of where ISON should
be and they'll try and image something. If no fragments
are surviving, or they are tiny, then Hubble will
not be able to find anything, but that negative
detection will tell us something: namely that ISON
is indeed gone for good."
ISON Photo Gallery
COMET LOVEJOY'S ACTIVE
TAIL: Amateur astronomers around
the northern hemisphere are reporting activity in
the tail of naked-eye Comet Lovejoy (C/2013 R1).
In Nagano, Japan, astrophotographer Kouji Ohnishi
could see big changes in less than an hour of monitoring:
Michael Jäger saw the same "disconnection
event" from his observatory in Masenberg,
Austria, on Dec. 5th. The disturbance could be caused
by a gust of solar wind or perhaps an episode of
vigorous outgassing in the comet's core.
Comet Lovejoy is now about as bright
as a 4th magnitude star. It is visible to the unaided
eye from the countryside and is an easy target for
backyard telescopes even in urban areas. Monitoring
is encouraged. Comet Lovejoy rises in the east just
before the morning sun. Sky maps:
Comet Photo Gallery
Space Weather Photo Gallery
Every night, a network
of NASA all-sky
scans the skies above the United States
for meteoritic fireballs. Automated software maintained
by NASA's Meteoroid Environment Office calculates
their orbits, velocity, penetration depth in Earth's
atmosphere and many other characteristics. Daily results
are presented here on Spaceweather.com.
On Dec. 8, 2013, the network reported
(5 sporadics, 1 Geminid)
In this diagram of the inner solar
system, all of the fireball orbits intersect at
a single point--Earth. The orbits are color-coded
by velocity, from slow (red) to fast (blue). [Larger
Potentially Hazardous Asteroids (PHAs
are space rocks larger than approximately 100m that
can come closer to Earth than 0.05 AU. None of the
known PHAs is on a collision course with our planet,
although astronomers are finding new
all the time.
December 9, 2013 there were 1446
potentially hazardous asteroids.
Notes: LD means
"Lunar Distance." 1 LD = 384,401 km, the distance
between Earth and the Moon. 1 LD also equals 0.00256
AU. MAG is the visual magnitude of the asteroid on
the date of closest approach.
official U.S. government space weather bureau
first place to look for information about sundogs,
pillars, rainbows and related phenomena.
call it a "Hubble for the sun." SDO
is the most advanced solar observatory ever.
views of the sun from NASA's Solar and Terrestrial
and archival images of the Sun from SOHO.
the NOAA Space Environment Center
underlying science of space weather