Metallic photos of the sun by renowned photographer Greg Piepol bring together the best of art and science. Buy one or a whole set. They make a stellar gift.
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SOLAR WIND: A minor solar wind stream is buffeting Earth's magnetic field. Arctic sky watchers should be alert for auroras. Aurora alerts: text, voice
SIGNIFICANT COMET PLUNGES TOWARD THE SUN: A comet nearly as wide as two football fields (200m) is plunging toward the sun where it will most likely be destroyed in a spectacular light show on Dec. 15/16. Although Comet Lovejoy (C/2011 W3) could become as bright as Jupiter or Venus when it "flames out," the glare of the sun will hide the event from human eyes. Solar observatories in space, however, will have a grand view. Yesterday the brightening comet entered the field of view of NASA's STEREO-B spacecraft:
"You can clearly see the comet heading diagonally through the images," says Karl Battams of the Naval Research Lab who prepared the animation. "During the 16-hour sequence, the comet brightens from magnitude +7.5 to +6, approximately."
It will soon grow much brighter. "This comet is a true sungrazer, and will skim approximately 140,000 km (1.2 solar radii) above the solar surface on Dec. 15/16," notes Battams. At such close range, solar heating will almost certainly destroy the icy interloper,creating a cloud of vapor and comet dust that will reflect lots of sunlight. The Solar and Heliospheric Observatory (SOHO) will have a particularly good view.
Discovered on Dec. 2nd by amateur astronomer Terry Lovejoy of Australia, the comet is an unusually large member of the Kreutz family. Kreutz sungrazers are fragments of a single giant comet (probably the Great Comet of 1106) that broke apart back in the 12th century. SOHO sees one plunging into the sun every few days, but most are small, no more than 10 meters wide. Comet Lovejoy is at least ten times larger than usual. Stay tuned for updates!
TOTAL LUNAR ECLIPSE: On Saturday, Dec. 10th, sky watchers across the Pacific witnessed a total eclipse of the Moon. During its hour-long transit through Earth's shadow, the Moon turned the color of the shadow itself--bright copper. The hue was meaningful to scientists who monitor lunar eclipses as part of their research on climate change. More on that below, but first regard this snapshot taken by James Barclay of Maidenwell, Queensland, Australia:
"The Moon looked like some alien planet hanging in a star-studded sky," says Barclay. "The excitement of those who witnessed this event will never be forgotten."
Dec. 10th Total Lunar Eclipse Gallery
Atmospheric scientist Richard Keen of the University of Colorado watched the event from Hawaii: "We had a fine warm morning for the eclipse here near Hale'iwa on Oahu'a North Shore. The eclipse was accompanied by the thunder of surf from the Banzai Pipeline, where later in the day surfers competed for the perfect ride," he says.
Keen wasn't just enjoying the view; he was also analyzing the event for scientific purposes. Lunar eclipses offer a unique way to assess the global dustiness of Earth's stratosphere. The scattering action of dust casts a red light into Earth's shadow. Lots of dust yields a deep red eclipse, while less dust produces a bright coppery hue.
The bright copper color of Saturday's eclipse suggests that the stratosphere is relatively clear. "My preliminary measurement of the brightness of the eclipse is magnitude -2.5 at mid-eclipse," says Keen. "It appears the clear stratospheric conditions of recent years is continuing."
This is important because the stratosphere affects climate; a clear stratosphere "lets the sunshine in" to warm the Earth below. At a 2008 SORCE conference Keen reported that "The lunar eclipse record indicates a clear stratosphere over the past decade, and that this has contributed about 0.2 degrees to recent warming."
The stratosphere has another effect on lunar eclipses. Note the soft blue colors in this picture from Shahrin Ahmad of Teluk Kemang, Malaysia:
This is the "turquoise fringe" often seen during total lunar eclipses. Keen explains: "Light passing through the upper stratosphere penetrates the ozone layer, which absorbs red light and actually makes the passing light ray bluer. This can be seen as a soft blue fringe around the red core of Earth's shadow."
More hints of turquoise may be found here, here and here.