Prepare yourselves: A rare “supermoon lunar eclipse” is coming

Just super.
Just super.
Image: AP Photo/K.M. Chaudary
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If you missed Jupiter’s collision with Venus back in June, now’s your chance to see another spectacular celestial sight—and this one should be much easier to spot. On Sept. 27, Earthlings will be treated to a “supermoon lunar eclipse,” a rare confluence of events that last occurred in 1982 and has been seen only five times since 1900.

The moon has an elliptical orbit, meaning it’s not always the same distance away from the Earth. When a full moon reaches its perigee—the point in its orbit when it’s closest to Earth—it can appear about 14% larger than average in the night sky. That’s known colloquially as a “supermoon,” and it happens a few times a year.

A regular moon, left, compared to a “supermoon,” right.
A regular moon, left, compared to a “supermoon,” right.
Image: Marco Langbroek/Wikimedia Commons, CC BY-SA 3.0

But to get the fabled supermoon lunar eclipse (we’ll shorten it to SLE from here on out), a supermoon must be combined with—you guessed it—a lunar eclipse. So when a full moon, at its perigee, passes directly into Earth’s shadow, an SLE is formed. And that happens only a few times a century.

Some astronomers aren’t thrilled with the “supermoon” moniker, arguing that it’s an extreme exaggeration of a relatively ordinary event. Here’s famed astrophysicist Neil deGrasse Tyson tweeting about a supermoon last year:

But an SLE gives the moon some characteristics that make it a little different from the average supermoon. Unlike a “blue moon,” which isn’t really blue, an eclipsed moon actually does change color. Sometimes it can appear almost blood red. At the very least, it should have a reddish-orange tint.

The next SLE will be in 2033, so you don’t want to miss it this year. According to EarthSky.org, the eclipse will begin at 9:07 pm EDT and should be visible in the Americas, Europe, Africa, and the Middle East. People in Alaska and western Asia might be able to see a partial eclipse in the early morning hours. Hopefully the skies will be clear.