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.
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STILL QUIET: 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 of M-class solar flares and a scant 1% chance of X-flares on Dec. 4th. Solar flare alerts: text, voice
GEMINID METEOR SHOWER: Earth is entering a stream of debris from rock 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. Meteor alerts: text, voice
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 upper 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. In the full-sized image, we also see just a trace of a 22o halo and stretching upwards from the sun a sun pillar."
"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."
Realtime Space Weather Photo Gallery
Realtime All-Comet Photo Gallery
Realtime Aurora Photo Gallery
Every night, a network of NASA all-sky cameras
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 15 fireballs.
(12 sporadics, 2 sigma Hydrids, 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 image] [movies]
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 ones
all the time.
On 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.
| ||The official U.S. government space weather bureau |
| ||The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| ||Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| ||3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| ||Realtime and archival images of the Sun from SOHO. |
| ||from the NOAA Space Environment Center |
| ||the underlying science of space weather |