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EARTH AT APHELION: Today, you are farther from the sun than usual. Earth's orbit around the sun is not a perfect circle, it's an ellipse, and on July 5th, Earth is at the most distant end of the curve. Astronomers call this "aphelion." When we are at aphelion, the sun appears smaller in the sky (by 1.7%) and global solar heating is actually a little less (by 3.5%) than the yearly average. This provides scant relief from northern summer heat; click here for reasons why.
BIG SOUTHERN SUNSPOTS: One of the biggest sunspot groups of Solar Cycle 24 is emerging near the sun's southeastern limb. AR1785 has a "beta-gamma-delta" magnetic field that harbors energy for powerful X-class solar flares. Another active region trailing behind it, AR1787, is only slightly less potent, with a magnetic field capable of M-class eruptions. NASA's Solar Dynamics Observatory photographed the sprawling complex during the early hours of July 5th:
These sunspots are a sign that the sun's southern hemisphere is waking up. For most of the current solar cycle, the northern half of the sun has dominated sunspot counts and flare production. The south has been lagging behind--until now. June brought a surge in southern sunspots, and the trend is continuing in July. This "southern awakening" could herald a double-peaked Solar Maximum due in late 2013-early 2014.
The largest dark cores in sunspot complex AR1785-1787 are as wide as Earth, making the ensemble an easy target for backyard solar telescopes. Amateur astronomers are encouraged to monitor developments, as NOAA forecasters estimate a 40% chance of M-flares during the next 24 hours. Solar flare alerts: text, voice.
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ELECTRIC BLUE: Observers of noctilucent clouds often describe their appearance as "electric blue." On July 3rd, Nature provided a color-check when a lightning storm erupted in Szubin, Poland, right in front of a noctilucent display. Marek Nikodem photographed the ensemble:
"I took the picture about 2 hours after sunset," says Nikodem. "This was an absolutely amazing evening." (Can't find the noctilucent clouds? Click here.)
The pale blue colors of the two phenomena are similar, but the resemblance is superficial. Lightning is hot, a genuinely electric discharge that heats the air to 30,000o C or more. The high temperature of the lightning's plasma (ionized air) gives it the same blue color as a hot O-type star. On the other hand, noctilucent clouds are cold, made of ice that crystallizes at the edge of space where the air temperature is -160o C. The tiny ice crystals in noctilucent clouds scatter blue light from the setting sun, which accounts for their lightning-like color.
2013 is shaping up to be a good year for noctilucent clouds (NLCs). The clouds surprised researchers
by appearing early this year, and many bright displays have already been recorded. Once confined to the Arctic, NLCs have been sighted in recent years as far south as Utah, Colorado, and Nebraska. They might spread even farther south in 2013.
Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped 6o to 16o below the horizon. If you see luminous blue-white tendrils spreading across the sky, you've probably spotted a noctilucent cloud.
Realtime Noctilucent Cloud Photo Gallery
[previous years: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2011]
SPACE WEATHER BALLOON CLIFFHANGER: On July 2nd a recovery team reached the payload of a space weather balloon launched on June 30th. It was the second attempt to retrieve the balloon from its mountainous landing site in the Sierra Nevada mountains of central California. The first attempt late on July 1st was aborted due to challenging terrain and fading sunlight. This time, the team started earlier and in the full light of midday they found the landing site. It turned out to be a cliffhanger:
As shown above, the payload was dangling from a shear cliff face more than 1400 feet above the foot of the Nevahbe Ridge. Super-climber Michael White, a member of the Earth to Sky Calculus student group that launched the balloon, was able to reach the landing site and snag the payload from the safety of a small ledge just above the parachute. The shoe in the photo belongs to Michael.
This balloon was launched at the peak of a record-setting heat wave in the southwestern USA, bringing temperatures as high as 128 F to desert areas around the launch site. The goal of the curiosity-driven flight was to discover whether the heat wave extended all the up to the Edge of Space. To help answer the question, the balloon's payload was outfitted with two HD video cameras, a pair of GPS trackers, a GPS altimeter, a cryogenic thermometer and an ozone sensor.
Students are analyzing the footage and data now. Stay tuned for results!
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