Let’s hope and pray we have clear skies tonight, May 15. It will be our last chance to see a primetime, early evening, total lunar eclipse, or “Blood Moon,” until May 2029. The eclipse begins just before 9:30 p.m. and will be over by 1 on Monday morning.
Lunar eclipses occur when the moon, in its orbit around the Earth, passes through the Earth’s shadow opposite the sun, also known as the umbra shadow. It should be quite a show as the moon takes on a ruddy hue during totality. Lunar eclipses can only happen during a full moon when our planet lies in a line between the sun and moon. But, this doesn’t occur every full moon because the moon’s orbit around the Earth is tilted by 5 degrees to the Earth’s orbit around the sun. Most of the time, the full moon misses the Earth’s shadow. It either passes above or below it. Not this time, though! This Sunday evening, the moon forges right into Earth’s shadow.
Right around 9:28 p.m., you’ll start to see the lower left side of the moon begin to darken, and by 10 p.m., you’ll really see a big bite taken out of the moon. You can’t help but notice that the shadow has a circular edge as it creeps across the lunar surface. Ancient Greek scientists saw this circular shadow of the Earth as proof the Earth was round. They were really ahead of their time.
From 10:28 p.m. until 11:54 p.m., the moon will be totally eclipsed but will still be visible. It will take on a bright orange or maybe bloody red hue. No one can really predict what shade the eclipsed moon will sport. Only the shadow knows! The Earth’s umbra shadow, that is. The umbra shadow opposite the sun is not totally dark because some of the sun’s light manages to pass through Earth’s atmospheric shell.
If you were standing on the moon during a total lunar eclipse, the Earth would be black except for a reddish ring that would circle the entire globe. That ring is lit up by the strained sunlight that makes it through the Earth’s atmosphere and is bent in the moon’s direction. All of the blue and yellow components of the sun’s light are scattered away by Earth’s atmosphere leaving just the reddish component of the sun’s light. The shade of the red light bathing the moon depends on the combined atmospheric conditions of where the sunlight is getting through.
No matter what shade of red the moon takes on, it’ll be beautiful and perfectly safe to view. Unlike solar eclipses, you don’t have to take precautions, although anytime you stare at a full moon it could affect you. It might make you a little loony!
A total lunar eclipse. (Mike Lynch)
Seriously, though, it’s a beautiful experience to watch a total lunar eclipse, and through a pair of binoculars or a telescope it’s even more fun. During totality you’ll see the moon pass in front of, or eclipse, several stars. Not only does the moon rise in the east and set in the west just like the sun, it also takes a much faster eastward migration among the background of stars as it orbits the Earth every month. It’s usually hard to see these stellar eclipses because of the moon’s brightness, but with the moon going through a one-hour plus “power failure,” they’re a lot easier to see. Because the moon has no atmosphere, you’ll see stars popping out of view on the eastern side of the moon’s disk and popping back into view on the western side.
Get a nap in so you can stay up for the entire Bloody Moon Party!
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can contact him at [email protected].
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