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Red Moon Rising

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Credit & Copyright: Stephen Barnes February 2, 2000 -- On January 20, 2000, the full moon plunged into the darkest part of Earth's shadow and put on a beautiful show for sky watchers from Europe to Hawaii.

"Hey, you were right, there really is an eclipse," exclaimed an amazed 8-year old observer in windy St. Louis, Missouri. "This is awesome!"

To that young sky watcher, the sight of the Earth's shadow taking a bite out of the brilliant lunar disk banished thoughts of the cold and transformed the night sky into something dynamic and spellbinding. It was also much-needed proof that his uncle (the author) was a genuine astronomer. As we craned our necks for a better view of the Moon, everyone in our little party of star gazers agreed that the eclipse was well worth the discomfort of a freezing winter breeze.

Less than an hour later the entire lunar disk was tinged with an eerie copper color. The surrounding stars, which were lost in the brilliant glare of moonshine earlier that evening, twinkled brightly in the crisp, clear mid western sky.

Right: These digitally superimposed photographs were captured by Stephen Barnes during the January 20, 2000 lunar eclipse. There are three exposures: one just as the Moon entered the Earth's shadow (top), once when the Moon was near the middle of the shadow, and once just before the Moon exited (middle). [more information]

Blue Sky, Red Moon

For many observers, the most striking aspect of the eclipse was the Moon's reddish hue during totality. During an eclipse, when the Moon is in Earth's shadow, there is a little bit of sunlight that passes through our atmosphere. White light from the sun is composed of all the colors of the rainbow, but our atmosphere treats different colors differently. Blue-colored light is scattered in all directions by airborne molecules. This is the same phenomenon that causes our sky to be blue. Red-colored light, on the other hand, is scattered very little. However, it is refracted (bent) inward toward the Moon. Red light that hits the Moon is reflected back toward Earth, so that we see the Moon glowing red during totality. If the Earth did not have an atmosphere, the Moon would be nearly black during a total lunar eclipse.

see caption


Above: When the Earth is situated precisely between the Sun and the Moon, why isn't the Moon totally dark? It's because of Earth's atmosphere. The white light from the Sun is a mixture of all the colors of the rainbow. When a ray of "white" sunlight passes at grazing incidence through Earth's atmosphere, molecules in the air scatter the blue light in all directions (this is why the sky is blue). The remaining reddish light is bent (refracted) into the Earth's umbral shadow zone, giving the eclipsed Moon a coppery glow. [more information]

see caption Differing amounts of clouds and volcanic aerosols in the Earth's atmosphere make each lunar eclipse appear differently. The 1991 eruption of Mount Pinatubo in the Philippines filled Earth's atmosphere with particulate matter and aerosols. As a result, until the air cleared in 1998, every total lunar eclipse between 1992 and 1997 (there were 6 of them) exhibited a darker-than-usual red coloration.

Right: This sequence of images was obtained by Doug Murray, a Science@NASA reader in Palm Beach Gardens, FL, during the January 20, 2000 total lunar eclipse.

The January 2000 eclipse was the first one since 1993 that was visible from start to finish across North America. This won't happen again until December 21, 2010.

If you missed this eclipse, there's another one just around the corner. On July 16, 2000 observers on the west coast of North America, the Pacific, Australia and Japan will see a spectacular eclipse with nearly two hours of totality.

image credit and copyright Doug Murray


Above: This unusual picture is a composite of a 2.5 hour exposure and a 2 hour exposure of the January 20th eclipse using a 1955 Rolleiflex Twins Lens Reflex 120 format camera. Doug Murray, a Science@NASA reader, captured these images from his front yard in Palm Beach Gardens, Florida. The Earth's rotation caused the Moon and stars to appear as streaks during the two exposures. As the Earth's shadow engulfed the Moon, the Moon streak became less and less bright, practically disappearing during totality. At this time, the Moon, which normally shines by reflecting direct sunlight, shone only by sunlight refracted through the Earth's atmosphere.

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Total Lunacy - Science@NASA article about the first lunar eclipse of the year 2000.

Total Lunar Eclipse: January 20-21, 2000 - a press release from the Goddard Space Flight Center

More information about the eclipse -from Fred Espenak at the Goddard Space Flight Center

Tips for photographing a lunar eclipse -an excellent overview from MrEclipse.com

5000 year catalog of lunar eclipses -During the 50 century period, 2000 B.C. to 3000 A.D., Earth experiences 12186 lunar eclipses.