NEW YEAR'S AURORA FORECAST: The New Year could begin with a geomagnetic storm. NOAA forecasters say there is a chance of G1-class storming on Jan. 1, 2018, when a stream of solar wind is expected to buffet Earth's magnetic field. A full Moon on the same date will bathe Arctic landscapes in a silvery glow, contrasting beautifully with green auroras overhead. Free: Aurora alerts.
ACTIVE COMET PANSTARRS: Distant comets, sailing quietly through the cold recesses of the solar system beyond Mars, usually don't change much from night to night. Comet PanSTARRS (C/2016 R2) is different. It's changing by the hour. Click to play a 2-hour movie recorded on Christmas night by astrophotographer Michael Jäger of Jauerling, Austria, and watch what happens to the indicated cloud:
The movie shows a whole section of the comet's tail disconnecting and billowing away. Jäger has been tracking this comet for months, and this kind of activity is not unusual. On multiple occasions since November, he has recorded blobs moving away from the nucleus as well as apparent activity in the comet's inner jets--each time in just a few hours. Comet PanSTARRS (C/2016 R2) is remarkably active.
What's happening? Sunlight could be vaporizing fragile ices in the comet's core, exposing caverns of sublimating gas and puffing clouds into space. Or the comet might be experiencing magnetic storms. Magnetic storms in comet tails have been observed before--most famously in 2007 when NASA's STEREO spacecraft watched a CME crash into Comet Encke. Encke's tail was ripped into forms akin to those Jäger has been seeing in Comet PanSTARRS (C/2016 R2). Given the quiet state of solar activity, however, the former hypothesis seems more likely.
Comet PanSTARRS (C/2016 R2) is currently moving through the constellation Taurus, shining with the integrated brightness of an 11th magnitude star. This means it is a suitable target for large backyard telescopes equipped with modern deep-sky cameras. Experienced observers like Jäger may be able to see more action in the nights ahead. Monitoring is encouraged.
POLAR STRATOSPHERIC CLOUDS: Are we heading for a outbreak of polar stratospheric clouds (PSCs)? Winter has barely begun, yet sky watchers around the Arctic Circle have already witnessed several colorful apparitions. Moreover, the clouds appear to be spreading to lower latitudes. On Dec. 23rd, Alan C Tough saw their aurora-like colors peeking through a gap in ordinary rainclouds over Elgin, Scotland, a full 10 degrees below the Arctic Circle:
The next night, Dec. 24th, Ivo Dinsbergs saw them from Riga, Latvia--like Tough's sighting, they were 10 degrees below the Arctic Circle. "Type I PSCs are not very often visible at these latitudes," says Dinsbergs. "The last time when they were observed in Latvia was 7 years ago."
Polar stratospheric clouds are a sign of extraordinarily cold temperatures in the stratosphere. Colorfu PSCs require temperatures around -85º C to form. The stratosphere is drier than almost any desert on Earth. Only when the air up there becomes profoundly cold do widely-spaced water molecules coalesce to form ice crystals--the "stuff" of PSCs. High-altitude sunlight shining through these ice particles produces the clouds' characteristic bright iridescent colors.
In recent years, some photographers sending their images to Spaceweather.com have expressed their impression that PSCs are appearing earlier in winter and spreading over a greater range of latitudes. So far, the polar stratospheric clouds of 2017-2018 are conforming to those reports. Stay tuned for more sightings as northern winter deepens.
GREEN CHRISTMAS: Some people wish for a White Christmas. In Abisko, Sweden, aurora tour guide Sarah Skinner was hoping for a different color: Green. "I got my wish!" she says. "I headed out with my Lights over Lapland group on Christmas night, and we were bathed in auroras for more than 3 hours." At the peak of the display, the whole landscape turned green:
"I will never forget this tour," she says. "There were bright auroras overhead, one guest enjoying their birthday and, to top it off, a marriage proposal. Christmas doesn't get much better than that!"
The reason for the display, and possibly the marriage proposal, was the solar wind. A stream of gaseous material flowing from a hole in the sun's atmosphere hit Earth on Christmas Eve, causing energetic particles from space to rain down on our planet's upper atmosphere. Green auroras were observed all around the Arctic Circle. Free: Aurora alerts.
EXTENDED! STUDENT CHRISTMAS SPECIAL: For the holiday season only, we're reducing the cost of payload space on Earth to Sky Calculus balloons from $500 to only $299. Buy a ticket to space on or before Jan. 1st and your student can send an experiment, photo, or keepsake item to the stratosphere, completely supported by an Earth to Sky Calculus launch and recovery team.
This is not only a great Christmas gift, but also a good kickstarter for science fair projects. Experiments will be flown and returned along with video footage, GPS tracking, temperature, pressure, altimetry and radiation data.
To take advantage of the discounted rate, payment must be received before Jan. 1st. However, the flight can take place at any time in the next 12 months.
Conditions: No mammals. Plants and non-pathogenic microbes are allowed. Generally speaking, experiments should weigh less than a few hundred grams and occupy a volume less than that of a school lunchbox. A brainstorming session is included with each certificate. Dr. Tony Phillips and other members of the Earth to Sky team will chat with recipients to help them craft an experiment that will work in the harsh environment of the stratosphere.
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All proceeds support hands-on STEM education