The dark, inner
shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a
circular cross section most easily seen during a lunar eclipse. And on the night of September 7/8 the Full Moon passed near the center of Earth’s umbral cone, entertaining eclipse watchers around much of our fair planet,
including parts of Antarctica, Australia, Asia, Europe, and Africa. Recorded
from Zhangjiakou City, China, this timelapse composite image uses successive
pictures from the total lunar
eclipse, progressing left to
right, to reveal the curved cross-section of the umbral shadow sliding across the Moon. Sunlight scattered by
the atmosphere into Earth’s umbra causes the lunar surface to appear reddened
during totality. But close to the umbra’s edge, the limb of the eclipsed Moon
shows a distinct blue hue. The blue eclipsed moonlight originates as rays of sunlight pass
through layers high in the upper stratosphere, colored by ozone that scatters
red light and transmits blue. In the total phase of this leisurely lunar
eclipse, the Moon was completely
within the Earth’s umbra for about 83 minutes.
Image & info via APOD
Image Credit & Copyright: Wang Letian (Eyes at Night)
Source: The Umbra of
Earth – Scents of Science
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