In one exhilarating moment in the predawn hours of August 15, 1977, it seemed as if the universe was sharing a tantalizing secret with us. That evening, the Big Ear radio observatory at Ohio State University recorded an incredibly strong and narrowband signal from the depths of outer space, which lasted 72 seconds. That enigmatic signal, lacking the normal telltale marks of natural astrophysical phenomena, earned the sobriquet Wow! After SETI’s observer admitted 2 days after the signal appeared on the paper and wrote “Wow!” It has ever since proved to be one of the most compelling mysteries of extraterrestrial intelligence.
Ever since, over the past decades, the Wow! signal has given rise to various theories, from comet radiation to human-made radio interference. Some have even gone so far as to suggest it could be a message from an advanced extraterrestrial civilization. But now, a novel hypothesis put forth by a triad of astronomers might finally provide one that is more down to Earth.
In a recent preprint, Abel Méndez, director of the Planetary Habitability Laboratory at the University of Puerto Rico, and his colleagues, it is proposed that the Wow! signal could have originated from the interaction of a magnetar flare with some cold, dense cloud of hydrogen gas floating between the stars. It caused this cloud to emit the radio wave burst, which was subsequently picked up by Big Ear. “I would say, wow—I never thought of that. I never thought of the Wow! signal as being real and being produced by some weird astrophysical phenomenon,” remarked Méndez.
The hypothesis of the researchers is still hypothetical and not yet peer-reviewed. Co-author Kevin Ortiz Ceballos, a graduate student at the Center for Astrophysics | Harvard & Smithsonian, added that the team is not yet claiming this is definitively the case. These are insights that powerfully direct them to an exciting possibility that they hope to chase.
The prime candidate for an artificial origin, the one prime candidate of the Wow! signal has always been that it was at a narrowband, focused on the 1,420 MHz frequency. Neutral hydrogen naturally emits radio waves at that frequency, making it such an obvious choice for radio astronomers—human or otherwise—searching for a universal base for communication. This further fueled speculation about the signal’s origin.
Méndez and his team therefore looked into the matter by fishing through archival records of the now defunct Arecibo Observatory. As such, they were somewhat surprised to find more than a dozen narrowband signals—all fairly near to the 1,420 MHz frequency—, including one which essentially matched the timing of the Wow! signal yet was hundreds of times fainter. The results add considerable weight to the possibility that the burst was of natural—and likely interstellar—origin.
The researchers are proposing that one such cloud was struck by a magnetar flare and erupted in an intense narrowband shine. That type of shine is known as a master, and it’s extremely rare though not unique. How that could come to be in space is not clear, adds the report. “I like this creativity,” Michael Garrett, chair of the International Academy of Astronautics’s SETI Permanent Committee, said, although he added that the idea seems a bit forced.
Despite the fresh interesting hypothesis, though, most astronomers shrug it off with skepticism. Yvette Cendes, a radio astronomer from the University of Oregon, pointed out that this narrowband characteristic of the Wow! signal still interferes with coming from human-made sources the most likely. She admitted herself, however, on the other hand, that the Wow!-like signals intercepted by Arecibo do breathe some new life into the new theory.
In the end, the mystery of the Wow! signal grows ever stronger among both scientists and the public. While this new proposition surely does provide a felicitous path going forward in caroming toward the goal line of future propositions, it also promotes what we feel is the likely complexity and wonder of the universe. As Méndez quipped, “every tantalizing hint of alien whispers” often turns out to be a misunderstood echo of esoteric astrophysics. At the moment, the inquiry into true proof of extraterrestrial intelligence continues on the strength of hope that someday the “wow” will convert into a “eureka.”