Bundle up and look up
Published 8:43 am Thursday, January 3, 2019
The moon has a special surprise in store. On the night of Jan. 20, and sliding across midnight, North American sky watchers will be treated to a total lunar eclipse.
Lunar eclipses differ from solar eclipses. A solar eclipse happens when the new moon passes between the earth and the sun. When viewed from terrestrial locations along a narrow path, the moon’s dark orb completely covers the solar disk, resulting in a total solar eclipse. From nearby regions, the moon doesn’t cover the sun completely. If you remember the solar eclipse of August 2017, which was partially visible from Farmville, you’ll no doubt recall that you needed special eye protection because viewing it involved looking directly into the daytime sun.
By contrast, a total lunar eclipse occurs at night when the earth passes between the full moon and the sun at an angle that causes the earth’s shadow to cross the face of the moon. When a lunar eclipse occurs, it can be seen from any location on earth where the moon is above the horizon. And, because viewers see only reflected sunlight, no special eye protection is needed.
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A lunar eclipse progresses in stages as the moon moves into and through the shadow cast by the earth. That shadow consists of two parts. The outer portion, in which the sunlight is only partially obscured, is called the penumbra. The central, darker core of the shadow is called the umbra. The eclipse’s first stage occurs when the moon enters the penumbra, and its face dims slightly, almost imperceptibly. The second stage, when the moon begins to move into the umbra, is more dramatic. The shadow will seem to take a dark nibble out of the edge of the moon. As the moon enters more deeply into the umbral region, the nibble grows into a full bite. The dark region continues to grow until just a thin crescent of moonlight remains. When the moon moves fully inside the umbra, the crescent vanishes and the lunar eclipse reaches the total stage.
During this stage, a strange thing happens. Instead of going completely black, the moon turns a coppery orange color. This happens because sunlight striking the earth at the outer fringes of its daylight side is bent by the atmosphere. Some of the refracted light, which features the same predominantly red hues that color sunrises and sunsets, penetrates the umbral shadow and casts a dim glow onto the face of the moon. The moon then reflects that light back toward the earth. Because the atmospheric conditions that scatter and absorb light are ever changing, every total lunar eclipse is unique in the extent of its coloration and brightness.
If you’d like to see the coming total lunar eclipse from Farmville, here’s a schedule of the main events: The earth’s shadow will begin to encroach onto the face of the full moon around 10:34 p.m. the night of Jan. 20. The moon will be fully eclipsed from about 11:41 p.m. until about 12:44 p.m. The earth’s shadow will continue to move on, unveiling the moon’s face as it departs, fully exiting about 1:51 a.m. in the wee morning hours of Jan. 21.
Eclipse watchers can also enjoy other nearby winter constellations. During the eclipse, the moon will be relatively high in the sky. If you stand looking toward the south, two bright stars under the moon will form a fairly straight line toward the horizon. The uppermost of these two is Procyon, the main star in the constellation Canis Minor (the Little Dog). The lower and brighter is Sirius, located in Canis Major (the Big Dog). Sirius is actually the brightest star in the entire night sky. These two dogs belong to their celestial master, Orion the Hunter. He stands ahead of them to the right and is most easily identified by the three stars in a row that form his belt.
Although the eclipse will last only a few hours and the moon will move on to its other phases and locations, the night sky offers ceaseless beauty. Pick any clear night, bundle up, step outside and look up. The heavens are hovering just above your doorstep.
KAREN BELLENIR has been writing for The Farmville Herald since 2009. Her book, Happy to Be Here: A Transplant Takes Root in Farmville, features a compilation of her columns. It is available from PierPress.com. You can contact Karen at kbellenir@PierPress.com.