Tuesday, June 13, 2017

"Wow!" Signal a Comet?

It's one of the most famous stories in the search for extraterrestrial life. In 1977, astronomers working with a large radio telescope in Ohio recorded a mysterious signal from space. It fit all the criteria for a likely alien communication, and while it was brief, the transmission was extremely strong. It was dubbed the "Wow!" signal, after a notation on the data printout made by one of the astronomers. But over the years, the signal became less of a "Wow!" and more of a mystery.

Radio telescopes have scanned the same area of the sky for decades and recorded nothing even remotely similar, which doesn't exactly shout "aliens." At the same time, astronomers had yet to work out any natural phenomenon that could have produced the signal. So it became a staple of extraterrestrial conspiracy books and the like. But now, a Russian astronomy professor may finally have worked it out. According to a recent paper, the signal was generated by a particular comet.

The signal was so strong and focused that the professor on duty during its discovery, Jerry Ehman, saw the monster signal on the printout, circled it and wrote “Wow!”— thus bestowing upon the signal a name which has stuck. Since then, however, telescopes have aimed themselves at the Wow! signal’s origin and turned up nothing. But now a new scientific paper from St. Petersburg College astronomy professor Antonio Paris may have solved the four-decade mystery once and for all.

So what’s the likely culprit of the Wow! Signal? A comet.

The Center for Planetary Science, which Paris helps run, previously put forth the notion that a passing comet and its tailing cloud could be the possible source for the Wow! signal. Indeed, comet 266/P Christensen —which was not yet known to astronomers at the time that the Wow! signal was recorded— is predicted to have been in the same region in the sky in 1977 where the Wow! signal was recorded.

To test this hypothesis, the Center pointed a 10-meter radio telescope at comet 266/P Christensen and recorded the signal. Over 200 observations, they saw a signal appear at precisely the same frequency as the Wow! signal, which disappeared when moved even 1° away from the comet.The resulting paper, recently published in the Journal of the Washington Academy of Sciences, provides a compelling answer to the mystery of the Wow! signal.

Not only did Paris' paper propose a mechanism, it also suggested a series of experiments that could be done to prove it. And so far, the experiments have worked. One more series of tests is scheduled for 2018, so we'll see how those go. Obviously, they will need to replicated a few times to make sure, but if the signal really is that strong, obvious, and easy to find just by pointing at the right comet, replication should pose no difficulty.

Some astronomers are skeptical of Paris' results, including Jerry Ehman - the guy who actually wrote "Wow!" on that printout. He doesn't think it was aliens, though. He's convinced it was some other sort of naturally occurring radio burst that we have yet to track down. His issue is that while Paris' comet may produce similar signals, based on the comet's path in 1977 the signal should have repeated once and lasted longer than it did. So replication and peer review will have to sort this one out, which really is as it should be.

As usual, the headline from Salon is a little hyperbolic. After forty years, there aren't that many people outside the conspiracy crowd who consider the "Wow" signal the "best hope" for alien life. It did seem that way to many at the time, but a lot of years have passed since then. It might have been out "best hope" if it had shown up multiple times from the same location and seemed to encode any complex data.

But it was a single, brief powerful signal - and most of the time those are just natural anomalies of some sort. Space is weird, after all.

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