Was the Legendary "Wow!" Signal Caused by a Comet, Rather Than ET?

Radio Telescope Scans the Sky

If you ask a scientist if there's any evidence of contact with extraterrestrial civilizations, you'll likely get the answer "none", but also with the caveat of "although there is the 'Wow!' signal, which hasn't yet been explained". This anomalous radio signal was detected just once, forty years ago, by Ohio State University's Big Ear radio telescope, and got its name from the annotation that astronomer Jerry R. Ehman scribbled on the computer printout when he noticed it: "Wow!"

Beyond simply being an anomalous signal that stood out from the usual background noise, the other important facet of the Wow! signal was its frequency: at the beginnings of SETI, it was theorised that any signal sent by E.T. might be located around the natural emission frequency of the most common element, hydrogen, which is 1420 megahertz. The Wow! Signal frequency was 1420 megahertz.

But now the media is trumpeting that "the Wow! signal has officially lost its wow factor". The alien-killing headline is based on a new paper, "Hydrogen Line Observations of Cometary Spectra at 1420 MHz", authored by Professor Antonio Paris. Building on his 2016 paper arguing that a comet and/or its hydrogen cloud might have been the cause of the Wow! signal, Paris now claims to have found actual examples of similar signals emanating from comets, based on 200 observations conducted between November 2016 and February 2017:

This investigation discovered that comets 266/P Christensen, P/2013 EW90 (Tenagra), P/2016 J1-A (PANSTARRS), and 237P/LINEAR emitted radio waves at 1420 MHz. In addition, the data collected during this investigation demonstrated there is a well-defined distinction between radio signals emitted from known celestial sources and comets, including comet 266/P Christensen.

We speculate that the strength of the original signal in 1977 would have been accounted for by the size of the Big Ear Radio Telescope (when compared with Site B) and/or the potential loss of mass from comet 266/P Christensen, which would have been considerably larger 40 years ago. In addition, while neutral hydrogen clouds have been observed around other comets (mostly from Lyman alpha spectra), determining the physical extent and density of the clouds around comets 266/P Christensen, P/2013 EW90 (Tenagra), P/2016 J1-A (PANSTARRS), and 237P/LINEAR were not the purposes of this investigation. To dismiss the source of the radio signal as emission from comet 266/P Christensen, we repositioned the telescope away from the comet and conducted clear sky observations when the comet was not near the coordinates of the “Wow!” Signal. During these clear sky observations, we detected no significant radio signal at 1420 MHz.

These results led Paris to the conclusion that "cometary spectra are observable at 1420 MHz and that the 1977 “Wow!” Signal was a natural phenomenon from a Solar System body".

So is that the end for the legendary Wow! signal? Apparently not, as a number of astronomers have already responded to the paper with serious skepticism. In a post at r/astronomy, radio astronomer Yvette Cendes explains multiple reasons why the new paper "screamed bullshit to me" - from the obscure journal it was published in, through the strange choice of units used to measure the signal, to the lack of important details about the methodology. In the end, Cendes suggests there might be a very good candidate for what caused Paris's signals (though not the Wow! signal): the Sun:

There is something really radio bright that was within 20 degrees of these comets during the observations- the sun! The sun is the brightest radio source on the sky- it can be thousands of Jansky at these frequencies, if not more, and is frankly bright enough that you can even observe it with one of those little one foot satellite dishes if you know what you're doing. With such an incredibly bright source so incredibly close, it is very, very possible (if not probable) that a bright signal on a telescope of this size is not a genuine source, but the signal from the sun picked up in a side lobe. Hell, you would likely have side lobe issues observing that close to the sun on the best radio telescopes on Earth. Does this paper mention the possibility of this, or how he dealt with observing so close to the sun to make sure he wasn't just picking the sun up in a side lobe? Of course not.

You'll find further skepticism on this new comet theory in this post at Discover ("the signal isn’t bright enough or rapid enough to be a good fit to the Wow! signal"). Additionally, In the comments to the Reddit piece there's much concern about both Paris 'inflating' his reputation, and the fact that he has used Kickstarter to collect money for his research.

Astronomer Chris Lintott has assembled a list of questions that he, and other astronomers, have regarding this new paper that supposedly debunks the Wow! signal. As far as I know Paris has not answered them publicly yet (from his tweets it appears he is currently travelling, so understandable).

The irony of this story is that Paris is also a ufologist (he is the founder and director of Aerial Phenomenon Investigations), and he's the one debunking the Wow! signal while orthodox astronomers are defending it as an ongoing mystery.

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