You are viewing the page for Dec. 21, 2011
  Select another date:
<<back forward>> -- News and information about meteor showers, solar flares, auroras, and near-Earth asteroids
Solar wind
speed: 383.7 km/sec
density: 4.2 protons/cm3
explanation | more data
Updated: Today at 2344 UT
X-ray Solar Flares
6-hr max: C2
2243 UT Dec21
24-hr: C4
0455 UT Dec21
explanation | more data
Updated: Today at: 2300 UT
Daily Sun: 21 Dec 11
Growing sunspot 1382 is beginning to crackle with C-class solar flares. Credit: SDO/HMI
Sunspot number: 139
What is the sunspot number?
Updated 20 Dec 2011

Spotless Days
Current Stretch: 0 days
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
Since 2004: 821 days
Typical Solar Min: 486 days

Updated 20 Dec 2011

The Radio Sun
10.7 cm flux: 137 sfu
explanation | more data
Updated 20 Dec 2011

Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Planetary K-index
Now: Kp= 1 quiet
24-hr max: Kp= 2
explanation | more data
Interplanetary Mag. Field
Btotal: 7.1 nT
Bz: 4.2 nT south
explanation | more data
Updated: Today at 2346 UT
Coronal Holes: 21 Dec 11
There are no large coronal holes on the Earthside of the sun. Credit: SDO/AIA.
NOAA Forecasts
Updated at: 2011 Dec 21 2200 UTC
0-24 hr
24-48 hr
10 %
10 %
01 %
01 %
Geomagnetic Storms:
Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2011 Dec 21 2200 UTC
0-24 hr
24-48 hr
05 %
05 %
01 %
01 %
01 %
01 %
High latitudes
0-24 hr
24-48 hr
15 %
15 %
10 %
10 %
05 %
05 %
Wednesday, Dec. 21, 2011
What's up in space

Don't just watch shooting stars. Wear them! Authentic meteorite jewelry for Christmas is now available in the SpaceWeather Store.

Meteorite jewelry

DECEMBER SOLSTICE: Tonight is the longest night of the year in the Northern Hemisphere and the shortest night in the Southern Hemisphere. The December Solstice, which marks the change of seasons, occurs at 12:30 a.m. on the 22nd EST (9:30 p.m. on the 21st PST) when the Sun reaches its farthest point south on the celestial sphere. Happy Solstice!

THE AMAZING TAIL OF COMET LOVEJOY: Widespread reports of Comet Lovejoy's tail are being received from around the southern hemisphere. The ghostly plume emerges just before sunrise, jutting vertically upward into the eastern sky ahead of the sun.

"I observed the comet with my unaided eye for 55 minutes this morning," says Colin Legg of Mandurah, Western Australia. "I also captured a timelapse sequence of the comet rising as twilight progressed." Click on the image to set the scene in motion:

"In the image you can see 2 tails," notes Clegg. These are the dust and ion tails. The gaseous ion tail is blow almost directly away from the sun by the solar wind, while the heavier, brighter dust tail more closely follows the comet's orbit.

The visibility of both tails could improve in the days ahead as the comet moves away from the sun and the background sky darkens accordingly. Early-rising sky watchers should be alert for this rare apparition. [finder chart]

more images: from Steve Chadwick of Himatangi Beach, New Zealand; from Chris Picking of Wellington, New Zealand; from Paulo Morales Valdebenito of San Francisco de Mostazal, Chile; from Kosma Coronaios of Louis Trichardt, Limpopo Province, South Africa; from Willian Souza of Sao Paulo, Brazil; from Grahame Kelaher of Perth, Western Australia; from Minoru Yoneto of Queenstown, New Zealand;

THE SUN IN A BEER CAN: "I have captured the sun in an empty beer can," reports Jan Koeman of Kloetinge, the Netherlands. In June 2011, Koeman assembled a solargraph--a simple pinhole camera consisting of a beer can lined with photographic paper--and for the past six months he has used it to record the sun's daily motion across the Dutch sky. Today he removed the photo-paper for inspection:

"This is what a photo with an exposure time of nearly 6 months looks like," says Koeman. The highest arcs were traced by the summer sun of June 2011. The lowest arc was made just today, Dec. 21st, on the eve of the 2011 winter solstice. Occasional gaps are caused by clouds.

Curiously, Koeman had more than one empty beer can to work with on that hot summer day in June when he began his project, so there are multiple views to enjoy. Click here for more solargraphs.

6-month Solargraph How-to Guides: #1, #2, #3

Dec. 10th Total Lunar Eclipse Gallery

  Near Earth Asteroids
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 21, 2011 there were 1272 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:
Miss Distance
2011 YQ1
Dec 14
1 LD
33 m
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
49 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.
  Essential web links
NOAA Space Weather Prediction Center
  The official U.S. government space weather bureau
Atmospheric Optics
  The first place to look for information about sundogs, pillars, rainbows and related phenomena.
Solar Dynamics Observatory
  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
Solar and Heliospheric Observatory
  Realtime and archival images of the Sun from SOHO.
Daily Sunspot Summaries
  from the NOAA Space Environment Center
  the underlying science of space weather
Science Central
Trade Show Displays
  more links...
©2010 All rights reserved. This site is penned daily by Dr. Tony Phillips.
©2019 All rights reserved.