Photo by: Haitong Yu

Haitong Yu

The Wow Signal: No, It Wasn’t Aliens

On a typical muggy midwestern August evening in 1977, astronomers at the Ohio State University’s Big Ear radio telescope got a big surprise. It was a signal so loud that it could only be described with one word: “wow!”

December 10, 2020

Don’t believe me? That word was so important that the astronomer who was reviewing the data a few days later, Jerry R. Ehman, wrote it on the printout next to the signal.

Hence: The Wow! Signal.

In all respects, the signal really was remarkable. It lasted for only about 72 seconds, appearing to originate from somewhere in the direction of the constellation Sagittarius. It was thirty times stronger than the background radio hum of the rest of the sky. It was at a radio frequency forbidden from use by anyone on Earth, reserved purely for astronomical observations. It was nearly at a frequency that neutral hydrogen naturally emits.

It was never seen again.

Of course, it’s tempting to think of the Wow! Signal as a sign of an alien civilization trying to talk to us. And despite happening over 40 years ago, that mysterious radio blast is in the news again, this time as an amateur astronomer has used a catalog of stars to find a potential source of the signal.

The ESA’s Gaia mission has cataloged nearly a billion stars, planets, comets, asteroids, and quasars across the universe. And it turns out that one of those identified stars, 2MASS 19281982-2640123 (sorry about the long name but that’s all we’ve got), happened to be near the direction of the supposed origin of the Wow! Signal back in 1977.

So, What is 2MASS 19281982-2640123?

2MASS 19281982-2640123 is a pretty unremarkable star, which makes it interesting: it’s roughly the same mass, brightness, and age as our sun. Which means any planets orbiting it at the right distance could be a potential home for life. Which means any intelligent critters living on one of those planets could have sent the Wow! Signal in our direction.

The trouble with this news story (and the Wow! Signal in general) is that it’s so tempting to jump on the alien hypothesis that it’s easy to start ignoring other possibilities. The astronomer behind the latest study only looked for sun-like stars in the Gaia data and skipped over any other possible source. So naturally there’s going to be a juicy news story here, rather than something much less engaging.

The biggest problem when trying to connect the Wow! Signal to aliens is that it’s never happened again–ever. Multiple searches with multiple telescopes over multiple decades have never seen the same signal repeated, in that patch of the sky or anywhere else. If it was aliens trying to contact us, it was the ultimate cosmic butt-dial: they rang once but never followed through.

Still a Mystery



Photo by: Haitong Yu

Haitong Yu

Ultimately, we’re not exactly sure what caused the Wow! Signal. Observations of 2MASS 19281982-2640123 have revealed that it’s…just another sun-like star in the galaxy, doing nothing interesting or out of the ordinary. The Wow! Signal could have terrestrial origins (people have broken the rules of radio before, after all), it could have been a fluke in the telescope system (which happens all the time), or it could be some flash of crazy physics in the universe (which happens all the time too). Either way, it’s likely that we’ll never know.

Hey, it’s good to have a few mysteries left in the universe, right?

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

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