Backyard Observatory

Everything You Need to Know About Supermoons

The good, the bad, and everything else there is to know about supermoons.

No, it's not pressing a ham against the driver side window while cruising the interstate. The supermoon has become a familiar sight in the news, if not the sky. When one rolls around people tend to talk about it, debate the name, and encourage you to see it with your own eyes. 

Since the moon is the brightest object in the night sky, a supermoon is incredibly easy to spot. Plus, they happen with relative frequency, at least compared to celestial events like a total lunar eclipse or meteor shower outburst. Because of those two factors, it's worth knowing exactly what it is you're looking at in the night sky. 

What is a supermoon?

A supermoon is the name given to a full moon that is at or near the part of its orbit that is closest to the Earth.

The moon orbits the Earth in an ellipse, so it is not always the same distance from the Earth. During every 27-day orbit, the moon reaches its apogee (the part of orbit furthest from the Earth) and its perigee (the part of orbit closest to the Earth). When a full moon occurs at or near the perigee, you have a supermoon. That full moon will appear slightly larger and brighter than an average full moon.

It's given the unofficial name of supermoon when it is within 90% of its closest approach to Earth. At that point, the moon appears to be 14% larger and 30% brighter than when the moon is near its apogee or the further point of its orbit from the Earth. 

Why is the name controversial?

Many astronomers and scientists have been vocal about saying the moniker is, more or less, stupid, even though the term has fully entered the lexicon at this point. There are even pop songs named after the event. 

The complaint is that "super" is hyperbolic. The moon is larger and brighter at perigee-syzygy (the technical term), but, as noted by NASA, "a 14% increase in the apparent size of something that can be covered with a fingernail on an outstretched arm won’t seem significantly bigger."

"Super," detractors contend, is a strong description for something that's just a little enhanced. If Superman were super by this standard, he'd probably be more accurately dubbed Above Average-Man. 

Nevertheless, a supermoon is larger and brighter, and it's worth enjoying any space event that reminds us to look up and think about the enormity of the universe. So, don't get too worked up over the name. If you enjoy seeing the moon at its largest and brightest, it's a damn good occasion to be outside, looking up at the night sky.

Ready to go stargazing?

Here are all the best stargazing events that you can get out and see this month or you could stay in a stream the northern lights from home. If you're just getting started, check out our guide to astronomy for beginners

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Dustin Nelson is a Senior Staff Writer at Thrillist. Follow him @dlukenelson.