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MAY AURORAS: Sky watchers in Alaska and Canada should be alert for auroras after nightfall on May 1st. That's when Earth is expected to run into a solar wind stream flowing from a coronal hole on the sun.
BIG SUNSPOT: More than four years after solar maximum, the sun continues to produce big sunspots. One is transiting the solar disk today: sunspot 756. It's about five times wider than Earth and poses a threat for M-class solar flares. (continued below)
Sunspot 756, April 25th - 30th. Credit: SOHO.
Sunspot 756 is big enough to see with the naked eye, but do not stare at the blinding sun. Try building a safe solar projector instead.
"Sunspot group 756 looked promising when it first appeared on April 25, and it didn't disappoint, growing larger each day," says Jörgen Blom of Stockholm, Sweden, who has been making daily sketches of the giant 'spot:
more images: from Jérôme Grenier of Paris, France; from Pavol Rapavy of Rimavska Sobota, Slovakia; from Ron Wayman of Tampa, FL; from Gary Palmer of Los Angeles, CA; from Sylvain Weiller of St Rémy les Chevreuse, France; from Didier Favre of Los Angeles, CA.
RAINBOWS IN THE NIGHT: It was a dark and stormy night in Great Falls, Montana, around 2 o'clock in the morning on April 27th when Jonathan Logan snapped these two pictures 20 seconds apart:
Notice anything strange? It's the rainbow. Rainbows are made of raindrops and sunlight, but at 2 o'clock in the morning there is no sunlight. The solution: this is a lunar rainbow. Behind the photographer's back, a nearly-full Moon was shining brightly. Moonbeams illuminated raindrops beneath the crackling thunderhead, forming a rare and beautiful rainbow in the night.
BONUS: April 24th Lunar Eclipse Gallery