SUNSET PLANETS: The brightest planets in the night sky are aligning for a must-see show in late February and March 2012. You can start looking tonight. [video] [full story].
QUIET SUN: Considering the fact that Solar Maximum is only about one year away, the sun is experiencing some remarkable spells of quiet. One of them is underway right now. There have been no significant flares for more than five days, and the sun's X-ray output has flatlined:
What's going on? In fact, solar activity is on the rise. For instance, an X-class solar flare on Jan. 27th triggered the strongest solar radiation storm since 2005. Also, auroras have been sighted recently as far south as Virginia and Oklahoma. The quiet interregnums are a sign that the current solar cycle, while active, is not quite as strong as other solar cycles that preceded it--like a mild hurricane season in the Gulf of Mexico. According to this point of view, temporary spells of low activity are to be expected. On the other hand, some researchers believe the quiet holds greater significance; it could foreshadow a major drop in solar activity. This is controversial, however, because forecasting the 11-year solar cycle is still an infant science. Indeed, surprises may be in the offing. Stay tuned for updates.
SPY-SAT DISAPPEARING TRICK: US spy satellite Lacrosse 5 occasionally confounds observers by disapppearing: In a matter of seconds, it can fade more than three astronomical magnitudes. Is this a deliberate form of stealth? Most experts think not, but no one outside of classified circles knows for sure what is going on.
To investigate, French astrophotographer Thierry Legault used his satellite-tracking telescope to photograph Lacrosse 5 as it sailed 490 miles above Paris on Jan. 15, 2012, and he caught the spysat in the act of disappearing:
"During the passage, the brightness of the satellite decreased by 10 times in only 4 seconds (a loss of 2.5 magnitudes)," describes Legault. "After 33 seconds of [dark flight] it regained its original brightness. Lacrosse 5 often shows this very singular behaviour, which is called by other observers (especially Marco Langbroek) the 'disappearing trick.'"
Other Lacrosse satellites do not perform the same trick, at least not to this extent, suggesting that the design of Lacrosse 5 differs from its predecessors. The fade is likely caused by some sort of self-shadowing--e.g., maybe some part of the spacecraft such as its solar panels casts a shadow over the main body when the spysat changes attitude.
Even Legault's fine images do not reveal the answer. "The cause of the disappearing trick, as well as the precise shape of the satellite, remain unknown."
Readers, would you like to try catching the tricks of Lacrosse 5? Check SpaceWeather's Simple Satellite Tracker and Flybys App for local flyby times.
Solar wind
speed: 297.3 km/sec
density: 1.1 protons/cm3
explanation | more data
Updated: Today at 1335 UT
X-ray Solar Flares
6-hr max: B3 1015 UT Feb18
24-hr: B4 0512 UT Feb18
explanation | more data
Updated: Today at: 1300 UT
Daily Sun: 18 Feb 12
A sunspot is emerging at the circled location. Credit: SDO/HMI
Sunspot number: 53
What is the sunspot number?
Updated 17 Feb 2012
Spotless Days
Current Stretch: 0 days
2012 total: 0 days (0%)
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 17 Feb 2012
The Radio Sun
10.7 cm flux: 104 sfu
explanation | more data
Updated 17 Feb 2012
Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Credit: NOAA/POES
Planetary K-index
Now: Kp= 1 quiet
24-hr max: Kp= 1 quiet
explanation | more data
Interplanetary Mag. Field
Btotal: 6.1 nT
Bz: 1.4 nT north
explanation | more data
Updated: Today at 1336 UT
Coronal Holes: 18 Feb 12
Solar wind flowing from this coronal hole could reach Earth on Feb. 18-19. Because of the coronal hole's far-southern latitude, however, the corresponding solar wind stream could sail south of our planet, making little impact. Credit: SDO/AIA.
