Blue Fringe On The Edge

ח' באדר א' תשס"ח
Keolwulf 9

From Science at Nasa:

On Wednesday evening, February 20th, the full Moon over the Americas will turn a delightful shade of red and possibly turquoise, too. It's a total lunar eclipse—the last one until Dec. 2010.

A lunar eclipse happens when the Moon passes through the shadow of Earth. You might expect the Moon to grow even more ashen than usual, but in fact it transforms into an orb of vivid red.

Why red? That is the color of Earth's shadow.

The delicate layer of dusty air surrounding our planet reddens and redirects the light of the sun, filling the dark behind Earth with a sunset-red glow. The exact tint--anything from bright orange to blood red is possible--depends on the unpredictable state of the atmosphere at the time of the eclipse. "Only the shadow knows," says astronomer Jack Horkheimer of the Miami Space Transit Planetarium

While you're watching, be alert for another color: turquoise. Observers of several recent lunar eclipses have reported a flash of turquoise bracketing the red of totality.

"The blue and turquoise shades at the edge of Earth's shadow were incredible," recalls amateur astronomer Eva Seidenfaden of Trier, Germany, who took the picture shown during the European lunar eclipse of March 3-4, 2007. Dozens of other photographers have documented the same phenomenon.

The source of the turquoise is ozone. Eclipse researcher Dr. Richard Keen of the University of Colorado explains: "During a lunar eclipse, most of the light illuminating the moon passes through the stratosphere where it is reddened by scattering. However, 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, he says, as a soft blue fringe around the red core of Earth's shadow.

To catch the turquoise on Feb. 20th, he advises, "look during the first and last minutes of totality." That would be around 10:01 pm EST and 10:51 pm EST (7:01 and 7:51 pm PST).

Read the full article and see more graphics at the link above.

February 20 is the full moon of Keolwulf, the Initiate Moon of the days of the Old Ones, in this year of the witch, and Purim Katan in the Jewish calendar.