Are we alone? For a second on August 15, 1977, it actually appeared like the reply is likely to be no. That night time the Massive Ear radio observatory on the Ohio State College was blasted by a remarkably intense transmission from the sky. Lasting at the least 72 seconds and coming in on a particularly particular frequency, it didn’t seem to have any of the hallmarks of a pure astrophysical phenomenon. As a substitute it resembled what we’d anticipate from a synthetic supply.
The radio sign vanished as shortly because it had appeared, and neither it nor something fairly prefer it has ever been detected since within the lengthy, unrequited seek for extraterrestrial intelligence (SETI). Named the Wow! sign, after an exclamatory notice {that a} SETI researcher scrawled on a printout of the recording, numerous concepts have arisen that try to clarify it. Possibly it was unusual radiation from a comet. Many researchers argue it was more than likely some type of human-made radio interference. Or, simply possibly, it was a message from some staggeringly superior cosmic civilization—a chance that, even now, has not but been definitively dominated out—not for scientists’ lack of making an attempt, nonetheless.
The most recent rationalization emerged final week from a trio of astronomers in a preprint that has not but been subjected to look assessment. And sorry, as soon as once more, it’s not aliens. The researchers suspect that the Wow! sign was created when a flare from a hypermagnetized, hyperdense star referred to as a magnetar struck a chilly interstellar cloud of hydrogen fuel. The flare brought on the cloud to incandesce within the radio wavelength, and this fast-and-furious outburst was detected by Massive Ear.
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Lead creator Abel Méndez, director of the Planetary Habitability Laboratory on the College of Puerto Rico, for a few years dismissed the Wow! sign as a mere instrumental glitch. However after scrutinizing a number of considerably Wow!-like indicators discovered unexpectedly in archival knowledge from the late, nice Arecibo Observatory, he and his colleagues now suspect that the well-known yawp from 1977 was brought on by a really uncommon form of astrophysical anarchy.
“I might say, wow—I by no means considered that. I by no means considered the Wow! sign as being actual and being produced by some bizarre astrophysical phenomenon,” Méndez says.
Different astronomers applaud the contemporary try to resolve this longstanding puzzle. Precisely how this deep-space fracas would produce the Wow! sign just isn’t but totally understood, nonetheless. “It has promise, however the particulars are nonetheless fairly scant,” says Yvette Cendes, a radio astronomer on the College of Oregon, who was not concerned with the brand new work.
The researchers’ flare-meets-hydrogen-cloud story is “undoubtedly a bit speculative,” says research co-author Kevin Ortiz Ceballos, a graduate scholar of astrophysics on the Middle for Astrophysics | Harvard & Smithsonian. “We’re not saying that that is undoubtedly the case. We’re saying that it’s a really thrilling speculation.”
On the lookout for suspicious radio waves is a well-liked methodology of questing for aliens. The difficulty is and all the time has been that just about any unusual emission can in precept be defined as some rare-but-all-natural astrophysical phenomenon, from burping black holes to convulsing planetary atmospheres. The important thing factor that distinguishes “pure” from “synthetic” on this context—consider our personal terrestrial transmissions, as an example—is that the latter are typically narrowband, targeted in a really small swath of radio frequencies fairly than smeared throughout an enormous vary. Additionally they typically have a construction to them that deliberately encodes info.
Scientists looking out the celebs for such synthetic transmissions may be fairly tightly targeted themselves, typically preferring to scan a particular frequency: 1,420 megahertz. Impartial hydrogen, the best aspect there may be, naturally emits radio waves at this frequency, which is one thing that presumably all astronomers—human or in any other case—would learn about. (Moreover and extra fortuitously, 1,420 MHz lies in a skinny band of electromagnetic spectrum that, on Earth, is held off-limits from human transmissions by worldwide settlement.) This confluence of things makes the frequency a SETI favourite.
The Wow! sign was not solely a narrowband sign—it was additionally proper within the 1,420 MHz candy spot, and it was 30 instances extra intense than any noticed background noise. Its celestial provenance couldn’t be exactly positioned. It appeared to return from close to M55, a dense cluster of stars within the constellation Sagittarius, nonetheless. It had the look of one thing like an intentional transmission that is likely to be anticipated to repeat. However with only a single 72-second snippet in our knowledge banks, adopted by no additional detections from that area of the sky, no one might say for positive.
“The Wow! sign has all the time been divisive within the SETI group,” says Jason Wright, an astronomer at Pennsylvania State College, who was not concerned with the brand new work. “It’s quite common to get one-off indicators that one can’t utterly clarify.” And more often than not, Wright notes, such anomalies present hints that they’re instrument malfunctions or the interception of a weird-looking, human-made radio transmission.
Curious as to whether the Wow! sign was real or not, Méndez and his staff determined to see if they may discover something resembling it by digging by the archival knowledge of the now-defunct Arecibo Observatory, which for many years was humanity’s largest and most delicate single-dish radio telescope. To their shock, they unearthed “indicators that had been similar to what the Wow! sign appeared like,” Ceballos says—a number of narrowband radio emissions thrumming near the vaunted 1,420 MHz frequency. In whole, the staff’s evaluation revealed eight Wow!-like indicators that Arecibo had recorded in an about an hour’s price of observing time throughout temporary and intermittent scans of small, disparate patches of sky between February and Might 2020. Every of those indicators was at or extraordinarily near 1,420 MHz however at wherever from 50 to 100 instances much less depth than the one which blasted the Massive Ear almost a half century in the past.
Seeing so many spatially scattered Wow!-like indicators in such a short while suggests a pure origin—and the obvious perpetrator could be the innumerable clouds of 1,420-MHz-emitting impartial hydrogen that astronomers have lengthy recognized to be frequent in interstellar area. Maybe, Méndez and his coauthors counsel, the Massive Ear was coincidentally pointed at one such cloud on that fateful night time in the summertime of 1977. And since it had been bombarded by a strong supply of radiation, this usually frigid cloud was as an alternative shining brightly in 1,420-MHz radio waves.
To create such an intense radio burst, the preliminary salvo of radiation would have been savage. Even a supernova explosion cascading into the cloud and compressing it wouldn’t have sufficed: that will have unleashed loads of radio waves, however they’d have occurred over a broad vary of frequencies. As a substitute the staff posits {that a} directed burst of x-rays and gamma rays—maybe a flare from a magnetar—might have slammed into the hydrogen cloud with such staggering depth that the end result was a potent narrowband glow, which we registered as, nicely, “Wow!”
Such a vivid, directed emission of radio waves is called a maser (the radio equal of a laser). On this case, it’s a kind of hydrogen maser. Hydrogen masers in area are uncommon, however they’ve been noticed for a number of many years. None at 1,420 MHz have been definitively detected, although—and though such emissions have been made within the lab, and there may be some theoretical work partly explaining how they could naturally seem, astrophysicists figured this course of was extraordinarily unlikely to happen in area. This research means that it could possibly occur by some means in nature, but the precise particulars of the physics stay murky.
“I like this creativity,” says Michael Garrett, chair of the Worldwide Academy of Astronautics’s SETI Everlasting Committee, who was not concerned with the brand new work. “However it feels a bit contrived to me.” A number of inconceivable issues wanted to occur all of sudden: Massive Ear simply occurred to have been wanting on the actual snapshot of sky wherein a magnetar flare smashed right into a hydrogen cloud. And a hydrogen maser at that actual narrowband frequency—a celestial occasion which has in any other case by no means been noticed earlier than—was serendipitously produced in order that Massive Ear might detect it.
“It’s not unimaginable, for positive,” Cendes says, and the Wow!-like indicators picked up by Arecibo make the research authors’ case an intriguing one. For now, nonetheless, their speculation wants extra astrophysical concept work to underpin it and clarify how nature can manufacture this particular sort of maser. In the end, she says, the narrowband nature of the unique—a key hallmark of putative know-how—implies that some form of human-made radio interference is the extra possible rationalization.
After all, its narrowband characteristic might nonetheless imply that the Wow! sign’s origin is nonhuman know-how—an intentional transmission beamed from minds elsewhere within the Milky Means or past. So might it’s aliens in any case? “No, I don’t assume so,” Méndez says. Nothing else going bump within the night time has ever fulfilled SETI’s hopes for first contact, he notes, so why ought to this one be so completely different? Time after time, every tantalizing trace of alien whispers as an alternative proves to be a misunderstood echo of esoteric astrophysics. What begins with a “wow!” ends as a “meh”—up to now, anyway.
