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 sun's southern hemisphere is peppered with sunspots,
but none of them is actively flaring. Solar activity
remains low. NOAA forecasters estimate a 25% chance
solar flares and a scant 1% chance of X-flares
on Dec. 4th.
Solar flare alerts:
GEMINID METEOR SHOWER:
Earth is entering a stream of debris
comet 3200 Phaethon, source of the annual Geminid
meteor shower. Our planet is just dipping into the
outskirts of the debris zone now, so visual meteor
rates are low. Nevertheless, the Canadian Meteor
Orbit Radar (CMOR)
is starting to pick up echoes from Geminid meteoroids.
This Dec. 4th radar map shows a concentration of
activity in the constellation Gemini:
"The Geminids, still ten days
from their maximum, are very clearly visible in
the latest CMOR data," reports Prof. Peter
Brown of the University of Western Ontario, which
operates the radar.
In the radar map, the Geminid radiant
is labeled 'GEM.' A second nearby radiant labeled
'NOO' marks the location of the November omega Orionids,
a minor shower that peaks in early December.
The Geminids won't peak until Dec.
13-14 when Earth passes through the core of the
debris stream, but Brown thinks observers should
start looking now. "Glare from the nearly-full
Moon will interfere with the Geminid's maximum in
mid-December," he says. "This week, however,
the Moon is new. Observers should be starting to
see activity from this very strong shower."
Observing tip: The best time to
look is during the hours between midnight and dawn
when the constellation Gemini is high in the sky.
RARE V-SHAPED SUN
HALO: At the end of Thanksgiving
Day when the sun was setting over Sumterville, Florida,
Paula Phillips took a break from her meal, stepped
outside and saw something odd--a pair of luminous
'Vs' in the deepening twilight:
"I've never seen anything like
this before," says Phillips. "I photographed
the phenomenon with a simple small Samsung camera."
They're sun halos, caused by sunlight
shining through ice crystals. Atmospheric optics
expert Les Cowley explains:
"These two ‘V’ shaped halos,
one rare and one common, change
shape dramatically as the sun climbs,"
he says. "Near sunrise or sunset is the only
time to catch them like this. The lower ‘V’ is an
tangent arc from horizontal hexagonal prisms
of ice. The upper one is a rare sunvex Parry
arc from similar crystals that - strangely –
are fixed so that two prism faces are always horizontal.
full-sized image, we also see just a trace of
halo and stretching upwards from the sun a sun
"I find it odd that I saw this
in Florida!" continues Phillips. Yet Florida
has ice crystal, too. The atmosphere 5 to 10 km
above the Sunshine State is always cold enough for
water to freeze.
"Florida and other warm places get plenty
of halos--some of them exceedingly
rare," says Cowley. "Look for them
everywhere, winter and summer."
Space Weather Photo Gallery
All-Comet Photo Gallery
Aurora 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. 4, 2013, the network reported
(12 sporadics, 2 sigma Hydrids, 1
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 4, 2013 there were 1444
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