SuperMoons are not a thing

Media outlets such as Earth and Sky are saying that we are entering a “SuperMoon season,” with three SuperMoons in a row, on March 9, April 8 and May 7. Yet there’s no mention of this in any of the world’s astronomical publications. Something strange seems to be afoot.

Understanding what’s happening is actually simple. The Moon’s elliptical orbit ensures that it is continually changing its distance from us. Moreover, its orbital shape itself alters depending on whether its egglike long axis is, on any particular day, aimed toward the Sun.

The Moon’s changing distance is never noticeable to the eye. Even serious Moon-watchers cannot tell whether it’s closer or farther from us than average. So a lunar “near approach” (called “perigee”) is visually a non-event, and nobody except fishermen and others concerned with tides ever cared to keep track until a few years ago. That’s when someone created the term “SuperMoon” as a synonym for lunar perigee. The catchy label proved irresistible to many in the media, who started displaying banner headlines urging readers, “Don’t miss tonight’s SuperMoon!” Photographers jumped on the bandwagon with telephoto or Photoshopped images depicting truly enormous Moons. (Like this.)


The problem: There’s never anything to see. A perigee or “SuperMoon” looks like every other Full Moon. Nonetheless, some writers, apparently discontent with only having one SuperMoon every few years, reserved for times when the Moon comes especially close, have greatly expanded its use so that here we are now, supposedly beginning a season with three of them!

In order of nearness, the six closest Full Moons of 2020 are the ones in April, October, March, November, September and May, respectively. That one in May, distancewise, earns sixth place out of the year’s 13 Full Moons. It’s right in the middle. It’s the year’s average Full Moon in terms of nearness. So why would anyone call that a “SuperMoon?”  Yet there it is, the third member in this supposed springtime trio of them.

It’s no wonder the world’s astrophysicists – and the pages of my magazine, Astronomy – ignore that term. We regard it as a form of hype. After all, “super” explicitly means something extraordinary, as in Superman or Super Bowl. Yet here we have a very normal-looking Full Moon that could easily let down those who look up and then see nothing out of the ordinary. And as someone who very much wants people to gaze at the heavens, I feel that disappointment is the last thing astronomy needs.

So now you know why you’ll never see that term on this page.

Want to know more? To read Bob’s previous columns, click here. Check out Bob’s podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.