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AMAZING COMET PIX: NASA's STEREO-B spacecraft continues to beam back jaw-dropping photos of Comet Pan-STARRS, which has a beautifully structured tail. Some of the images show the comet dodging CMEs! Tune into the Twitter feed of comet expert Karl Battams for the latest images.
WILL THE SKY TURN GREEN ON ST. PATRICK'S DAY? A magnetic filament snaking around sunspot AR1692 erupted on March 15th at about 0600 UT. The slow explosion, which took hours to unfold, produced an M1-class solar flare and a bright CME. SOHO (the Solar and Heliospheric Observatory) photographed the expanding cloud, which is heading directly toward Earth:
The CME left the sun traveling some 900 km/s (2 million mph). Three-dimensional computer models based on observations from SOHO and NASA's twin STEREO probes predict the CME will cross the void between sun and Earth in two days or less. NOAA forecasters estimate a 70% chance of polar geomagnetic storms when the cloud arrives on March 17th. This means the sky could turn green on St. Patrick's Day! High latitude (and possibly even middle latitude) sky watchers should be alert for auroras this weekend. Aurora alerts: text, voice.
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THE MAGNITUDE OF COMET PAN-STARRS: "There seem to be a lot of pictures, but a shortage of magnitude estimates for Comet Pan-STARRS," says Richard Keen, professor of atmospheric sciences at the University of Colorado. "I saw it for the first time this evening, and got a magnitude estimate before the comet slipped behind a narrow cloud bank." Keen is an expert observer of astronomical brightness, especially that of lunar eclipses which he uses to study aerosols in the stratosphere. "The comet is magnitude +0.2 with a short, but bright vertical tail. It was quite visible to the unaided eye. After the [head of the comet] set behind the mountains, the tail was visible for two or three more minutes."
A growing number of observers say they can see the comet with their unaided eye. Here it is on March 14th at sunset over Valley Forge, PA:
"The comet looked fantastic through my 10x70 Fujinon binoculars, and it was barely visible to the naked eye," says photographer John Chumack. Note: "Barely visible" is an improvement over recent nights.
Visibility should continue to improve in the nights ahead as Pan-STARRS moves away from the sun. Keen's magnitude estimate of +0.2 means that the comet is approximately twice as bright as a first magnitude star. When it is framed by darker skies, it will really stand out. Tonight when the sun goes down, step outside, face west, and take a look: sky map.
More: NASA video, 3D orbit, ephemeris, light curves.
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