‘Wow!’ Signal Was…Wait For It…Comets

Article Updated: 5 May , 2016
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The Wow! signal. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)

The Wow! signal recorded on August 15, 1977. The ones, twos and threes indicate weak background noise. Letters, especially those closer to the end of the alphabet, represent stronger signals. The “6EQUJ5” is read from top to bottom (see graph below) and shows the signal rising from “6” to “U” before dropping back down to “5”. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)

Comets get blamed for everything. Pestilence in medieval Europe? Comets! Mass extinctions? Comets! Even the anomalous brightness variations in the Kepler star KIC 8462852 was blamed for a time on comets. Now it looks like the most famous maybe-ET signal ever sifted from the sky, the so-called “Wow!” signal, may also be traced to comets.

Say it ain’t so!

The Big Ear Observatory, on the grounds of Ohio Wesleyan University, operated from 1963-1998. It was part of Ohio State University's long-running Search for Extraterrestrial (SETI) program. The observatory was torn down in 1998 to make room for a golf course. Credit: Bigear.org / NAAPO

The Big Ear Observatory, on the grounds of Ohio Wesleyan University, operated from 1963-1998. It was part of Ohio State University’s long-running Search for Extraterrestrial (SETI) program. The observatory was torn down in 1998 to make room for a golf course. Credit: Bigear.org / NAAPO

In August 1977, radio astronomer Jerry Ehman was looking through observation data from the Ohio State’s now-defunct Big Ear radio telescope gathered a few days earlier on August 15. He was searching for signals that stood apart from the background noise that might be broadcast by an alien civilization. Since hydrogen is the most common element in the universe and emits energy at the specific frequency of 1420 megahertz (just above the TV and cellphone bands), aliens might adopt it as the “lingua franca” of the cosmos. Scientists here on Earth concentrated radio searches at and around that frequency looking for strong signals that mimicked hydrogen.

Ehman’s searches turned up mostly background noise, but that mid-August night he spotted a surprise — a vertical column with the alphanumerical sequence “6EQUJ5″ that indicated a strong signal at hydrogen’s frequency. Exactly as predicted. Big Ear picked up the signal from near the 5th magnitude star Chi-1 Sagittarii in eastern Sagittarius not far from the globular cluster M55.

Astonished by the find, Ehman pulled out a red pen, circled the sequence and wrote a big “Wow!” in the margin. Ever since, it’s been called the Wow! signal and considered one of the few signals from space that defies explanation. Before we look at how that may change, let’s make sense of the code.

Plot of signal strength vs time of the Wow! signal on August 15, 1977. Credit: Maksim Rossomakhin

Plot of signal strength vs time of the Wow! signal on August 15, 1977. The signal rose and fell during the 72 seconds observation window. Credit: Maksim Rossomakhin

Each digit on the chart corresponded to a signal intensity from 0 to 35. Anything over “9” was represented by a letter from A to Z. It was probably the “U” that knocked Ehman’s socks off, since it indicated to a radio burst 30 times greater than the background noise of space.

In Big Ear’s 35 years of operation, it was the most intense, unexplainable signal ever recorded. What’s more, it was narrowly focused and very close to hydrogen’s special frequency.

Big Ear listened for just 72 seconds before Earth’s rotation carried the signal’s location out of “view” of antenna.  Since the radio array had two feed horns, the transmission was expected to appear three minutes apart in each of the horns, but only a single one ever picked it up.

Despite follow-up observations by Ehman and others (more than 100 studies were made of the region) the signal was gone. Never heard from again. Nor has anything else like it ever been recorded anywhere else in the sky.

Careful scrutiny eliminated earthbound possibilities such as aircraft or satellites. Nor would anyone have been transmitting at 1420 MHz since it was within a protected part of the radio spectrum used by astronomers and off-limits to regular broadcasters. The nature of the signal implied a point source somewhere beyond the Earth. But where?

On August 15, 1977, periodic comets 266P/Christensen and 335P/Gibbs would have both been very close to the small swath of sky south of Chi Sagittarii where the Wow! signal was received. Diagram: Bob King, source: Stellarium

On August 15, 1977, periodic comets 266P/Christensen and 335P/Gibbs would have both been very close to the narrow swath of sky south of Chi Sagittarii where the Wow! signal was received. Could they be implicated? Diagram: Bob King, source: Stellarium

If it really was an attempt at alien contact, why try only once and for so short a time interval? Even Ehman doubted (and still doubts) an extraterrestrial intelligence origin, but a much more recent suggestion made by Prof. Antonio Paris of St. Petersburg College, Florida may offer an answer. Paris earlier worked as an analyst for the U.S. Department of Defense and returned to the “scene of the crime” looking for any likely suspects. After studying astronomical databases, he discovered that two faint comets,  266P/Christensen and 335P/Gibbs, discovered only within the past decade, had been plying the very area of the Wow! signal on August 15, 1977.

A huge cloud of hydrogen surrounded Comet Hale-Bopp when it neared the Sun in the spring of 1997. Ultraviolet light, charted by the SWAN instrument on the SOHO spacecraft, revealed a cloud 100 million kilometres wide and diminishing in intensity outwards (contour lines). It far exceeded the great comet's visible tail (inset photograph). Although generated by a comet nucleus perhaps 40 kilometres in diameter, the hydrogen cloud was 70 times wider than the Sun itself (yellow circle to scale)

A huge cloud of hydrogen surrounded Comet Hale-Bopp when it neared the Sun in 1997. Ultraviolet light, charted by the SWAN instrument on the SOHO spacecraft, revealed that the cloud far exceeded the great comet’s visible tail (inset photo) —  70 times wider than the Sun itself (yellow circle to scale at right). Credit: SOHO (ESA & NASA) and SWAN Consortium / inset: Dennis di Cicco

If you recall, a comet has two or three basic parts: a fuzzy head or coma and one or two tails streaming off behind. Invisible to earthbound telescopes, but showing clearly in orbiting telescopes able to peer into ultraviolet light, the coma is further wrapped in a huge cloud of neutral hydrogen gas.

As the Sun warms a comet’s surface, water ice or H2O vaporizes from its nucleus. Energetic solar UV light breaks down those water molecules into H2 and O. The H2 forms a huge, distended halo that can expand to many times the size of the Sun.

Paris published a paper earlier this year exploring the possibility that the hydrogen envelopes of either or both comets were responsible for the strong 1420 MHz signal snagged by Big Ear. On the surface, this makes sense, but not all astronomers agree. First off, if comets are so radio-bright in hydrogen light, why don’t radio telescopes pick them up more often? They don’t. Second, some astronomers doubt that the signals from these comets would have been strong enough to be picked up by the array.

image of the full page of the computer printout that contains the "Wow!" signal. Credit:

Image of the full page of the computer printout that contains the “Wow!” signal. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)

A quick check on 266P and 335P at the time of the signal show them both around 5 a.u. from the sun (Jupiter’s distance) and extremely faint at magnitudes 22 and 27 respectively. Were they even active enough at those distances to form clouds big enough for the antenna to detect?

Paris knows there’s only one way to find out. Comet 266P/Christensen will swing through the same area again on Jan. 25, 2017, while 335P/Gibbs follows suit on January 7, 2018. Unable to use an existing radio telescope (they’re all booked up!), he’s begun a gofundme campaign to purchase and install a 3-meter radio telescope to track and analyze the spectra of these two comets. The goal is $20,000 and Paris is already well on his way there.

It would be a little bit sad if the Wow! signal turned out to be a “just a comet”, but the possibility of solving a 39-year-old mystery would ultimately be more satisfying, don’t you think?

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8 Responses

  1. Steven says

    Tricky way to get a modest sized astronomical radio dish… but a good cause to nail some things down with.

  2. michael1 says

    You can see what is wrong with science in america from this discovery. Nobody is interested in checking out the possible source as it would not make them higher in the pecking order of academia. This lack of followup is epidemic in the sciences. They have never found any aliens broadcasting on the hydrogen line so the source is coming from something else which might actually tell them something of how the universe works, instead they just ignore it like thousands of other finds. For example take the zika virus, they have evidence it is causing mutations in babies, has anybody started looking for a vaccine? Zero , zilch nada from any science organization and the Federal government as the money and prestige is researching and getting a paper out on the virus, not actually finding a prevention or cure.

  3. I was skeptical of this when I first read about it a few months ago. If that star chart is accurate, and the comets were that close together, well maybe. Be interesting to find out exactly how close they were to each other. Did their coma’s interact in some way that produced a brief signal? Seems a bit of a coincidence that an alien signal would pass directly between two comets on their way to Earth. Looking forward to the future research on this topic.

  4. jjb says

    First – as another poster stated, a great way to get a “Free”, radio telescope! I have to agree, and I’m honestly a little skeptical as to the complete motivation here. But hey .. as I’m very fond of saying:

    “Time is the teller of all tales great and small. Time is never too early and never too late. Time is always right on time.”

    Second – again, as also another poster stated, I was always surprised at the lack of follow-up and such of various science fields.

    Point: Why did it take 39 years for someone to ‘get here’? Something of this significance and yes it is significant … should have been well investigated, hey even 30 years ago!!

    But sadly, his “motivations” will be questioned and challenged and I can see why:

    * He wanted someone to pay for his new toy and this is what he came up with!

    It is a valid, very valid point.

    * Then the conspiracy nuts will have proof, he did / does work for the Government, DOD no less, and they will say this is a “set up” to “hide the truth” of alien life.

    Was it the comets? Hey could have been. Was it, a theory a few of us had back then, I’m 61. Was it a “Gravitational Bouncing Sound wave”, similar to gravitation lensing. Like water ripples, we might of say a “ripple” of the sound? Thus why it was not found again. The “ripple” died off.

    There is literally so much we do not yet understand about Deep Space, let alone our very own Solar System. We are still making new discoveries that blow old theories out the window ….

  5. jd01248 says

    Unfortunately, and little known obviously, the WOW signal has already been debunked. Some people may not believe it, but try this out for yourself.

    • BlackWolfStanding says

      When I go fishing, I have a depth finder. It gives me an accurate reading where the bottom of the lake is and where the fish are. If I start getting closer to land and in shallower water, I have to reduce the power or sensitivity of the depth finder or I get feed back. And suddenly instead of 50 feet of water, I’m actually in 10 feet of water.

      So what you are saying is the “WoW” signal is some form of feed back? And not really from deep space at all. Just normal communications from Earth bouncing off either the atmosphere or near Earth celestial objects?

      I thought that was ruled out pretty early in the process of trying to ID the “WoW” signal?

      • Patreon
        Aqua4U says

        I like to fish to! I live in middle northern Californicator and prefer fishing off the rocks along the coast. A somewhat dangerous occupation, sneaker waves are always a threat so it’s best to go with a buddy to keep more eyes on the waves… Biggest fish caught? How’s a 46″ 27lbs ling cod sound? Un-for-tuna-nettly.. those day are mostly history as water temps rise and Fukushima rads are here… Three eyed fishies? ACK!

  6. Patreon
    Aqua4U says

    Wait for it? Yes.. we’re waiting. Will confirmation of an ETI come from radio waves? I doubt it… It takes too long for radio signals to propagate across interstellar distances to make practical sense. There must be a better way? The use of quantum entanglement comes to mind, but that has been shown to be a more localized phenomena. https://www.sciencedaily.com/terms/quantum_entanglement.htm

    Our rapidly evolving sciences may yet find a way? A method to communicate over interstellar distances may be developed using the enormous potential of quantum computation in a super smart AI? How far off is that? Think about this: AI may already be happening in some lab somewhere? I expect that announcement to be made soon, which is another fine reason to read UT every day!

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