Tuesday, April 15, 2014

Orange Eclipse Across a "Pink" Full Moon

April 2014 lunar eclipse (c) John Ashley
Lunar eclipse of April 2014, photographed left to right at 16-minute intervals.
In the wee hours this morning, the sun, moon and Earth all lined up like school children. Because Earth was in the middle of the line, the sun cast Earth's shadow across the moon - an orange lunar eclipse of April's "pink" full moon. Pink refers to wild ground phlox, which is the first spring wildflower to bloom somewhere (though no one ever specifies where).

This composite photo shows the eclipse progression in paired images made at approximately 16-minute intervals, starting from the left. The familiar full moon (left and right bookends) glows before and after the eclipse. After the eclipse begins, you can either expose the camera for the sunny (upper left) or the shadowed (lower left) side of the moon. Halfway through, the totally eclipsed moon is a lovely shade of orange (center). On the right, the shadow images are above the sunny images. If you combine any pair, you would get a complete and detailed moon image. To my brain, all of this makes more sense visually than verbally. (To other brains, maybe not so much.)

The orange color during the eclipse comes from sunlight passing through Earth's stratosphere, where it gets scattered and reddened. Sunlight passing through the Earth's upper stratosphere, the ozone layer, absorbs red and passes turquoise-colored light on to the lower edge of the eclipsed moon; some cameras recorded a turquoise edge, but this color wasn't visible from northwestern Montana. (There's a lot more science to it. See here.) Also, this eclipse really wasn't a so-called "Blood Moon" because the upper atmosphere is currently clear, lacking in volcanic ash particles that would have darkened the Earth's shadow to red.

If you close your eyes and imagine you are standing on the moon during the eclipse, Earth would be surrounded by a ring of sunlight. Half of that light is sunset and half is sunrise, all at the same time. An unmanned NASA moon probe, Surveyor III, actually photographed this "ring of fire" during an eclipse (lunar from the Earth's viewpoint, solar from the moon's vantage) in April, 1967.

Today's event was the first of four eclipses this year, three of which are visible from Montana. October 8th will bring another total lunar eclipse to the Pacific Northwest, while October 23rd brings a partial solar eclipse to the western U.S.

NASA Eclipse Web Site