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CHANCE OF MAGNETIC STORMS: NOAA forecasters estimate a 20% to 40% chance of polar geomagnetic storms on Dec. 28-29 in response to the arrival of one or more CMEs. High-latitude sky watchers should be alert for auroras. Aurora alerts: text, voice.
ON MARS, TOO: Sunspot 1387 erupted on Christmas day, hurling a coronal mass ejection (CME) directly toward Mars. According to analysts at the Goddard Space Weather Lab, impact will occur on Dec. 30th at 1800 UT (+/- 7 hr). Click to view an animated forecast track:
Unlike Earth, Mars does not have a global magnetic field. Instead, the Red Planet has "magnetic umbrellas." These are fossil remnants of an ancient global magnetic field that decayed billions of years ago. When a CME hits Mars, the action happens in the umbrellas' canopies. Because the umbrellas are scattered around Mars, martian auroras can theoretically occur even near the equator.
Different world, different space weather.
MOTHER OF PEARL: As December draws to a close, the first polar straospheric clouds of northern winter are forming around the Arctic Circle. P-M Hedén photographed the phenomenon last night over Tänndalen, Sweden:
"Wow, what a lovely sight!" says Hedén. "They appeared in the sunset sky next to Venus and the crescent Moon."
Also known as "nacreous" or "mother of pearl" clouds, these icy clouds form in the lower stratosphere when temperatures drop to around minus 85ºC. Sunlight shining through tiny ice particles ~10µm across produce the characteristic bright iridescent colors by diffraction and interference.
"Nacreous clouds far outshine and have much more vivid colours than ordinary iridescent clouds, which are very much poor relations and seen frequently all over the world," writes atmospheric optics expert Les Cowley. "Once seen they are never forgotten."
more images: from Krystian Rosa of Brandbu, Norway; from Patricia Cowern of Porjus,Sweden
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 28, 2011 there were 1272 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Mag. | Size |
2000 YA | Dec 26 | 2.9 LD | -- | 80 m |
2011 SL102 | Dec 28 | 75.9 LD | -- | 1.0 km |
2011 WS95 | Dec 28 | 7.1 LD | -- | 46 m |
1991 VK | Jan 25 | 25.3 LD | -- | 1.9 km |
433 Eros | Jan 31 | 69.5 LD | -- | 8.5 km |
2009 AV | Feb 16 | 44.9 LD | -- | 1.2 km |
2000 ET70 | Feb 19 | 17.7 LD | -- | 1.0 km |
2011 CP4 | Feb 23 | 9.1 LD | -- | 255 m |
2008 EJ85 | Mar 6 | 9.1 LD | -- | 44 m |
1999 RD32 | Mar 14 | 57.9 LD | -- | 2.3 km |
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 |