Lunar Eclipse Here Sunday Evening

Celestial Lights

By Phyllis Burton Pitluga

The Full Moon rises soon after sunset on September 27, minutes before it begins to slip into Earth’s deep shadow. The Moon will be totally eclipsed for an hour and 12 minutes, between 9:11pm and 10:23pm.

As the Earth turns, the Moon rises in our sky. At the same time the Moon is orbiting eastward toward and through Earth’s shadow. Notice the coloration of the shadow on the Moon. The reddish color comes from the “edge” of the Earth where colorful sunrises and sunsets are occurring. Because this eclipse begins soon after sunset here in San Miguel, our skies are contributing to the coloration (or, if cloudy, to a darker shadow).

As the lunar eclipse progresses, the sky is more star-filled as the Sun’s light on the Moon is cut off by Earth itself. The Moon is orbiting in front of the stars of Pisces (the Fishes). Near mid-eclipse, the three bright stars of the Summer Triangle are high overhead. The Milky Way is spanning the sky from northeast to southwest. And Saturn is the brightest star-like object low in the southwest.

 

The accompanying diagram shows that, at the distance the Moon orbits, the Earth’s shadow is about three times the diameter of the Moon. The Moon is passing below center of the shadow during this eclipse. When the Moon is passing through the deep “umbra” shadow, the Moon is totally eclipsed with no sunlight reaching the surface. After 10:23pm, the Moon will be passing through the “penumbral” shadow until 11:27pm, where a partial eclipse is occurring on the Moon’s surface.

Phyllis Burton Pitluga is Astronomer Emerita from Chicago’s Adler Planetarium and Astronomy Museum and now a resident of San Miguel de Allende.

Illustration Credit: F. Espenak, NASA Goddard Space Flight Center

 

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