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SUNSPOT WATCH: The Sun has a rash--and it's getting worse. Small sunspots are popping up everywhere. The latest is active region 890, the second new sunspot in as many days. What's next? Stay tuned.
DA VINCI GLOW: Look west at the sunset tonight, behold the crescent Moon, and think of Leonardo Da Vinci. Almost 500 years ago, the Renaissance master solved an ancient mystery: What is that strange glow between the horns of the crescent? (continued below)
Above: Da Vinci's sketch of Earthshine in 1510 vs. amateur astronomer Riccardo Di Nasso's photo of Earthshine in 2006.
The mysterious glow, Da Vinci realized, is sunlight reflected from Earth onto the Moon: diagram. Now we call it "Earthshine" or better yet the "Da Vinci glow." Bask in it tonight: sky map.
more images: from Richard Bell of Kalamazoo, Michigan; from P-M Hedén of Vallentuna, Sweden; from Dennis Mammana of Borrego Springs, California;
GREEN RIM: "I was trying to capture the crescent moon, but the sky was murky with blowing dust," says Pete Strasser of Tucson, Arizona. "What I saw instead was a green rim along the top of the setting sun."
No, the sun isn't turning green. The emerald rim is caused by refraction: Earth's atmosphere acts like a giant lens, bending green light more strongly than red, so that the sun appears to have a thin green fringe at sunrise and sunset. Sometimes, steep gradients in air temperature magnify these fringes, resulting in a magnificent green flash.
more images: from Günther Strauch of Borken, Germany