Tonight’s Sturgeon Moon Supermoon isn’t rare, but worth a look

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Supermoons aren’t all that rare, astronomers say. But they’re still worth a look.

Weary astronomers have a message about supermoons: Scientifically speaking, the event is nothing to … moon over.

Coined in 1979, a supermoon describes a full moon that is “perigean” — when the Earth and the moon are at their closest point — said Wayne C. Foster, the planetarium educator at the Cernan Earth and Space Center in River Grove, Illinois. There are usually 12 full moons per year, but not all are supermoons.

“It’s a common misconception that the moon orbits around the Earth in perfect circles,” he said. “The moon actually has an elliptical orbit, so the distance between the Earth and moon changes over time.”

And how much closer to the Earth does a supermoon get? About 15,000 miles closer than its average place in the sky, Foster said.

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That makes it appear about 7 percent larger than usual and 15 percent larger than when the moon is farthest from Earth. Sounds impressive right? To the naked eye of the average stargazer, the difference is negligible. And for scientists who collect moon data, they use a satellite orbiting between 12 to 30 miles above the moon, called the Lunar Reconnaissance Orbiter, said Michelle Nichols, the director of public observing at the Adler Planetarium in Chicago. So the supermoon doesn’t offer them any new intel by its closer proximity to Earth.

There are supermoons that have a little something extra. The Aug. 11 Sturgeon Moon — named, per the earliest Farmer’s Almanacs, by Algonquin peoples who caught Great Lakes fish under August full moons — coincided with the annual Perseid meteor shower — a fly-over of debris from the Comet Swift-Tuttle. Saturn was also visible, reflecting at its near-brightest.

Does that qualify that supermoon to be super? Or maybe at least a notable moon? “It’s always special when multiple events happen at once, but it’s not necessarily uncommon,” Foster said. In fact, for astronomers and meteor enthusiasts, the timing is a little bit annoying: “The full moon’s light is going to wash out a lot of Perseid, meaning we’ll actually see fewer meteors,” Nichols said.

And what of the mythos of a full moon? The supposed link between supermoons and volcanic activity or earthquakes? Studies have repeatedly come back disproving any causation, Nichols said. The same goes with psychological studies of people behaving particularly madly under a supermoon’s influence.

“You’re noticing [this behavior] more because you’re aware that it’s a full moon,” Nichols said. “But look at all the actual numbers — they don’t hold up. “If you hold out a book at arm’s length, the force of that book on you is greater than the force of the moon on you.”

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But even if the “super” in “supermoon” is a bit of a hyperbole, it doesn’t mean that they shouldn’t be enjoyed or learned about.

“If a supermoon or moon name is what gets people out and looking at the moon, fantastic!” said Nichols.

In fact, Nichols has a challenge for readers to engage in supermoons, with a little citizen science: At home, devise a repeatable way to measure something about a supermoon — its brightness or size, Nichols suggests — and compare these characteristics to future moons.

“People are fascinated with the night sky and for good reason. Getting out and looking up is the most important thing,” said Foster.

Thanks to Alicia Benjamin for copy editing this article.