Wow historical! the signal may finally have a source. Sorry, it’s not aliens

The original Wow! the signal was detected decades ago by the Big Ear radio telescope at Ohio State University. As the telescope scanned the sky, a computer program converted the incoming radio signals into a series of letters and numbers representing their intensity and printed them overnight.

In the morning, astronomer Jerry Ehman and his colleagues would look at the prints for anything interesting. When Ehman saw a signal from the night of August 15, 1977, he recognized it as something extremely bright.

Even more intriguing, it was in a narrow wavelength range associated with neutral hydrogen atoms. Other astronomers interested in the search for extraterrestrial intelligence, or SETI, had suggested that this wavelength might be a natural calling frequency for alien civilizations. Ehman circled the signal and wrote Wow! in red pen border.

The signal was never seen again. Astronomers have suggested several non-alien explanations for the original, including comets in our solar system and intrusions from Earth-orbiting satellites or space debris. But none of them hold up completely.

In search of similar signals, Mndez and colleagues examined some of the last data received by the Arecibo radio telescope before it was decommissioned in 2020. (SN: 12/4/20). Between February and May 2020, the Arecibos antenna tracked the sky similar to what the Big Ear did in the 1970s, allowing researchers to directly compare the data.

Mndez didn’t expect to find much. I knew about Wow! signal for a long time, like everyone. But I rejected it, probably like many astronomers, as Mndez says. Not an astronomical event. And definitely even less, the aliens.

But to his surprise, the Arecibo data showed some signals that looked a lot like Wow! just faint. He realized that the signals corresponded to clouds of cold atomic hydrogen scattered around the galaxy.

I said: Wait, wait, wait! This was the moment, says Mndez. If there was a moment brighter, this would be it. That would be Wow! signal.

The next question was how to briefly illuminate the hydrogen clouds. The details still need to be ironed out, but Mndez and colleagues have an idea: A bright radio source, from something like a dead magnetized star, a magnetar, could set off a flare and destroy the cloud with energy. This energy can excite the hydrogen atoms in a special way and cause a laser effect, where all the atoms emit light at the same wavelength at the same time. (SN: 4/23/10).

This would be an unusual phenomenon, Mndez admits. Such hydrogen masers have been built in laboratories on Earth, but few have been observed in space, and none at this frequency. The perfect alignment of a magnetar, a cold hydrogen cloud, and the Big Ear would also have been lucky, although this could help explain why the signal was only seen once.

If this explanation turns out to be correct, it could pose a problem for SETI research (SN: 30.9.18). If astronomers ever detect another strong signal at this frequency, it would be unclear whether it was from aliens or glowing hydrogen clouds.

The SETI project has been looking for exactly this type of event, says Mndez. If we have a natural process that can produce it, it could be a false positive.

Modern SETI techniques probably wouldn’t be fooled by a hydrogen maser, says astronomer Jason Wright of Penn State, who was not involved in the new work. But he’s reserving judgment on the idea until the details of the mass effect are more fleshed out, which Mndez and colleagues plan to do in a follow-up paper.

It suggests a phenomenon that has never been observed, says SETI astronomer Jason Wright of Penn State, who was not involved in the new work. The set of physical conditions is extremely delicate and specific, and it is not clear whether this is even possible.

But even if Wow! signal was occurring naturally, it would be good, says Wright. False SETI results can lead to amazing science. For example, when astronomers first noticed pulsars, they called the rotating LGM stellar corpses Little Green Men (SN: 3/8/18). The seminal paper on their discovery devoted an entire section to the exclusion of ET.

They weren’t aliens, Wright says, but it was still a Nobel Prize.