COMET LULIN UPDATE: Experienced observers report that Comet Lulin has brightened to naked-eye visibility from dark-sky sites. It looks like a pale "fuzzy patch" in the constellation Libra before dawn. Backyard telescopes pointed at the patch reveal a lovely green comet with a rapidly re-growing plasma tail. Browse the gallery for latest photos.
DUSKY LUNAR ECLIPSE: On Monday, Feb. 9th, the full Moon will pass through the outskirts of Earth's shadow, producing a penumbral lunar eclipse. The event should be easily visible to the naked eye as a dusky shading of the northern half of the Moon. A similar eclipse in March 2006 looked like this:
Stefan Seip took the picture from Welzheim, Germany. Note the gray shadow, lower-right, intruding on what should be a uniformly-lit full Moon. This kind of eclipse is not as dramatic as a deep-red total lunar eclipse, but it does have a subtle, almost-surprising beauty which should not be dismissed until you've seen one with your own eyes.
Maximum eclipse occurs on Monday between the hours of 1400 and 1520 UT (6:00 am - 7:20 am Pacific time; 4:00 a.m. - 5:40 am Hawaii time). The timing favors observers in western North America, Hawaii, Australia and east Asia: visibility map.
More information: [animated eclipse] [NASA details] [photo gallery]
ICY CORONA: Colorful lunar coronas are formed by spherical droplets of water in clouds. Moonlight hits the liquid droplets and diffraction does the rest. At least, that's how it's supposed to work....
Last night, Prof. Joseph Shaw of Montana State University looked up and saw a lovely corona circling the Moon--but something was not quite right. The cloud that caused the display seemed too high and cold for water droplets. More likely, Shaw figured, it was a cloud of ice, and to test his hypothesis, he shined a laser into the heavens:
The timing and polarization of the laser's reflection revealed the cloud's altitude and composition. Just as Shaw suspected, it was high (7.5 - 10 km) and contained an abundance of ice crystals. Sharp-edged specks of ice, not spherical droplets of water, must have produced the corona.
"Ice crystals in clouds are usually much too large to produce visual diffraction patterns," says Shaw. "However, this was a special type of cloud--a 'wave cloud' created when air oscillates after flowing over mountains such as those that surround my town, Bozeman, Montana. Wave clouds have been found to sometimes contain little tiny ice particles created when liquid droplets freeze so quickly they have insufficient time to grow into large ice crystals."
The crystals in this particular wave cloud were 10 to 20 microns in diameter--perfect for making the corona Shaw observed.
"We are funded to measure clouds, aerosols and atmospheric radiation for climate studies," says Shaw. "Often I get to do studies like this when I recognize the opportunities that Mother Nature presents."
February 2009 Aurora Gallery
[Previous Februaries: 2008, 2007, 2006, 2004, 2003, 2002]
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