Saturday, 21 July 2012

What Was the Wow! Signal?

What Was the Wow! Signal?


Wow_signal2.jpg


By Patrick J. Kiger


Everyone remembers the Steven Spielberg’s 1977 classic sci-fi film “Close Encounters of the Third Kind,” which depicted an imagined first contact with an alien civilization. But most probably don’t realize that a few months before the movie came out,  real-life scientists believed—at least for a few exciting moments—that they might have detected an actual message sent by  extraterrestrials.

It was mid-August 1977, and across the U.S., many if not most people were focused on the shocking death of rock-and-roll great Elvis Presley at age 42. But in Ohio, a 37-year-old man named Jerry Ehman was transfixed by another startling event that—at least for searchers for extraterrestrial intelligence—potentially was even more momentous.

Ehman, a volunteer researcher for Ohio State University’s now-defunct Big Ear radio observatory, perused data from the telescope’s scan of the skies on August 15, a few days earlier. In those days, such information was run through an IBM 1130 mainframe computer and printed on perforated paper, and then laboriously examined by hand. But the tedium was shattered when Ehman spotted something surprising—a vertical column with the alphanumerical sequence “6EQUJ5,” which had occurred at 10:16 p.m. EST. He grabbed a red pen and circled the sequence. In the margin, wrote “Wow!”

Ehman’s excitement over that bit of arcane information stemmed from the Big Ear’s mission at the time, which was searching space for radio signals of the sort that might be emanated by extraterrestrial civilizations, if they were attempting to make contact with intelligent life elsewhere in the universe. To Ehman, this signal, which had come from the direction of the constellation Sagittarius, looked an awful lot like it could be such a message. Observatory director John Krauss and his assistant Bob Dixon, who subsequently examined the data, were similarly astonished by it.

But was it? More than three decades later, the Wow Signal, as it has come to be known to SETI researchers, remains both the first and best potential evidence of communication from extraterrestrials, and one of the most perplexing mysteries in science.  Over the years, Ehman and colleagues worked to rule out other explanations—such as satellites, aircraft or ground-based transmitters on Earth. But by the same token, researchers have yet to prove that it actually is message from space. “It’s an open question.” Ehman told the Columbus Dispatch in 2010. Or as the late science-fiction author Arthur C. Clarke once put it in a 1997 interview with New Scientist magazine, “God only knows what it was.”

To grasp the significance of the Wow Signal, it helps to understand what Ehman and his colleagues were looking for. Back in the early 1960s, Cornell physicists Philip Morrison and Guiseppe Cocconi had tried to figure out how a distant extraterrestrial civilization, if one existed, might try to contact others in the universe. First, they hypothesized, aliens would use a radio signal, since such transmissions require relatively little energy to generate and can travel huge distances across space. Second, they assumed that the aliens would be smart enough to pick a message that other intelligent species might understand, even if they spoke a very different language. Chemicals, they noted, emit distinctive electromagnetic frequencies, or signatures, which is how astronomers can determine the composition of distant planets and stars from their light. Since hydrogen, the most common element in the universe, emits a signal with a frequency of 1420 megahertz, they reasoned that aliens might send out a signal that mimicked it.

But the signal spotted by Ehman was the first that seemed to fit that description almost exactly.

Each digit on the printout represented the intensity of a radio signal, from zero to 35, with intensities over nine being represented by letters. Most of the signals on the printouts were ones and twos. But this one, as signified by the “U” in the middle, was extremely powerful—about 30 times greater than the ordinary ambient noise of deep space. Indeed, it was the loudest, longest signal that the Big Ear, which was shut down and dismantled in 1997, would ever pick up. And the signal was narrowly focused and extremely close to 1420 megahertz, the frequency of hydrogen. In contrast, natural sources of radiation, such as planets, usually send out a much broader range of frequencies.

While that all has seemed so tantalizing to SETI researchers, they’ve never been able to prove that the Wow Signal actually was such a message. And much about it was difficult to explain. Scientists also were puzzled when they traced the signal to a location northwest of the globular cluster M55—a spot where there apparently was no star or planet. SETI researcher Paul Shuch told New Scientist in 1997 that if the signal did come from an alien civilization, it would have required some amazingly advanced equipment. Assuming that the extraterrestrial beacon was the size of the biggest radio telescopes on Earth, the aliens would have required a 2.2 gigawatt transmitter, vastly more powerful than any existing terrestrial radio station [but within the range of HAARP-style installations – New Illuminati ed.].

But the most puzzling thing about the Wow Signal was that it lasted approximately 72 seconds, and never was detected again, even though in the 20 years that followed, scientists conducted more than 100 studies of the same region of sky. If aliens were trying to contact us, wouldn’t they keep repeating their message? Back in the early 2000s, researchers tried once more with a 26-meter radio telescope in Hobart, Tasmania, which was smaller than the Big Ear but more advanced technologically. Despite their ability to detect signals only five percent as strong as the Wow Signal, the Astrobiology Magazine reported in 2003 that they found nothing that resembled it.


From National Geographic @ http://channel.nationalgeographic.com/channel/chasing-ufos/what-is-the-wow-signal/

The 'Wow!' Signal: One Man's Search for SETI's Most Tantalizing Trace of Alien Life



By Ross Andersen
 

For decades, Robert Gray has been trying to duplicate the most surprising and still-unexplained observation in the history of the search for extraterrestrial life.



Late one night in the summer of 1977, a large radio telescope outside Delaware, Ohio intercepted a radio signal that seemed for a brief time like it might change the course of human history. The telescope was searching the sky on behalf of SETI, the Search for Extraterrestrial Intelligence, and the signal, though it lasted only seventy-two seconds, fit the profile of a message beamed from another world.

Despite its potential import, several days went by before Jerry Ehman, a project scientist for SETI, noticed the data. He was flipping through the computer printouts generated by the telescope when he noticed a string of letters within a long sequence of low numbers---ones, twos, threes and fours. The low numbers represent background noise, the low hum of an ordinary signal. As the telescope swept across the sky, it momentarily landed on something quite extraordinary, causing the signal to surge and the computer to shift from numbers to letters and then keep climbing all the way up to "U," which represented a signal thirty times higher than the background noise level. Seeing the consecutive letters, the mark of something strange or even alien, Ehman circled them in red ink and wrote "Wow!" thus christening the most famous and tantalizing signal of SETI's short history: The "Wow!" signal.
 
Despite several decades of searching, by amateur and professional astronomers alike, the "Wow!" signal has never again been found. In his new book, The Elusive Wow, amateur astronomer Robert Gray tells the story of the "Wow!" signal, and of astronomy's quest to solve the puzzle of its origin. It's a story he is well-positioned to tell. That's because Gray has been the "Wow!" signal's most devoted seeker and chronicler, having traveled to the very ends of the earth in search of it. Gray has even co-authored several scientific articles about the "Wow!" signal, including a paper detailing his use of the Very Large Array Radio Observatory in New Mexico to search for it. I spoke with Gray about the "Wow!" signal, radio telescopes, and the economics of prospective extraterrestrial civilizations.
 
 From a technical standpoint, what makes the "Wow!" signal so extraordinary?

Gray: The main thing is the profile of the signal, the way it rises and falls over about seventy-two seconds. When we point these big dish antennas up at the sky, and a radio source moves across them, they have a special signature, a kind of fingerprint. That fingerprint results from the "loudness" of the radio source slowly increasing, getting to a peak as the dish points straight at it, and then slowly decreasing as the object moves across the dish and past its beam of observation. In the case of the "Wow!" signal, the signal followed that curve perfectly. It looked exactly like a radio signal in the sky would look, and it's pretty unlikely that anything else---like an airplane or satellite or what have you---would leave a special signature like that. 

 Also there's not much doubt that the "Wow!" signal was a radio signal, rather than something from a natural source like a quasar. That's because Ohio State was using a receiver with fifty channels, which is sort of like having fifty AM radios, each tuned to adjacent stations. With the "Wow!" there wasn't any noise on any of the channels except for one, and that's just not the way natural radio sources work. Natural radio sources diffuse static across all frequencies, rather than hitting at a single frequency. So it's pretty clear that this was a radio signal and not a quasar or pulsar or some other natural radio source, of which there are millions. It was very narrow band, very concentrated, exactly like a radio station, or a broadcast, from another world would look. 


 The "Wow!" signal turned up very close to the frequency at which hydrogen glows. Why is that significant?


Gray: Well there's a little history there. In the early sixties when people started thinking about the possibility of detecting extraterrestrial broadcasts with radio telescopes, one of the first frequencies suggested was the frequency that interstellar hydrogen glows at. At the time, it was one of the few interstellar emission lines that was known, and a lot of radio observatories had a receiver that could pick it up so it was especially convenient to look for broadcasts there. 

If you imagine that there are all of these radio astronomers around the universe looking at the stars with big antennas, which is what you need to pick up a signal from that far, chances are that they too would be listening at the frequency of hydrogen, because there is so much of it around. It's the wave you can use to map the gas in galaxies, so it's a natural "channel" for astronomers to look at. There weren't a lot of frequencies that had that natural characteristic. So in the early decades of SETI, that's the frequency that most people chose to listen at. 

 By the way, not everybody agrees with this strategy now. A lot of new emission lines have been found, and so the current best practice is to listen to millions of frequencies at a time so you don't have to guess which one ET might favor. And that's exactly what NASA's SETI project tried to do, and that's what the Allen Telescope Array at U.C. Berkeley is trying to do. But it just so happened that the Ohio State people were using the hydrogen strategy when they found this thing, and, it just so happens that the "Wow!" signal was fairly close to where Hydrogen was dwelling. So if you believe the magic frequency strategy, that extraterrestrials would necessarily broadcast in the Hydrogen frequency, then the "Wow!" signal sort of fits that. 

  newverylargearraymagichour.jpg
The Very Large Array in New Mexico

 
Is it possible that the "Wow!" signal is somehow a computer glitch, or a signal from earth that was reflected off of space debris of some sort?

Gray: Of course it's possible. It could have been any number of things. However, it almost certainly wasn't a computer glitch, because it showed this rise and fall of intensity that's just exactly what a radio source from the sky would look like. Also, the Ohio State radio telescope was cleverly rigged to filter out local stuff.

 The only thing that conceivably could have made that special signature is a satellite of some sort at just the right distance, going just the right speed, in order to mimic a celestial object traversing the sky. So that's a possibility, but it seems pretty unlikely for a number of reasons. First, it would have been seen by a lot of people. Ohio State would have seen it repeatedly, because satellites broadcast repeatedly. Secondly, if it was a secret satellite it would have been pretty stupid to broadcast at a frequency that radio astronomers across the world listen to. 

For a long time, Jerry Ehman, who actually scribbled "Wow!" on the original computer printout, considered the possibility that it was a piece of space debris reflecting a signal from the earth back down into the antenna. But he no longer believes that to be the case. And I'm not saying that it definitely was an extraterrestrial broadcast; there's no proof of that. The best way I can think to analogize this thing is to say that it was a tug on the cosmic fishing line. It doesn't prove that you have a fish on the line, but it does suggest that you keep your line in the water at that spot.

 
Some have suggested that if the "Wow!" signal was alien in origin, then perhaps it sweeps around its home planet or star, the way light does from a lighthouse, which would explain why it hasn't yet reappeared. Do you think that's plausible?

  
Gray: That's my favorite theory. And it's just an idea of course. But when you step back from all of this a little bit, you notice that almost all searches for extraterrestrial intelligence have been surveys that look at all of these different spots in the sky for just a few minutes at a time. And the assumption such searches operate on is that there is a beacon, or a broadcast of some sort, that is on all the time, and so all you have to do is survey the sky and if it's there you'll find it. It's the easiest method, and it's the right thing to do when you're first starting out. 

But if you look at this in a deeper way, and you calculate the kind of energy it would take to operate a beacon that is on all the time, broadcasting in all directions, strong enough so you could pick it up from many, many light years away, the amount of power is enormous. It's in the range of thousands and thousands of big power plants. We humans certainly couldn't do something like that now. So to have a signal that's always there, you have to assume a very advanced intelligence, and you have to assume that it's highly motivated to talk to us, and neither of those things may be true of a broadcaster. They might not be so rich, or profligate with their energy, or, for that matter, very interested in talking. They might use some other cheaper strategy---brief periodic broadcasting, a sweeping lighthouse beam, or other methods. 

 As you may know, there's another thrust in SETI, which has become the focus of a lot of people's interest over the past ten years and that's optical SETI, where you look at starlight and see if you find any sudden, brief, flashes of light that are much stronger than what the star normally puts out. The idea is that you might find extraterrestrials communicating by shining a giant laser at us, and it's an idea that's become quite popular. But as with most SETI projects, they're simply scanning the sky, looking at each spot for roughly a minute. And at the end of a couple of years they can tell you they've looked at every spot in the sky and they didn't see any flashes, but of course there you have the same problem as you do with radio surveys. You look in every direction, but you only do it for a couple of minutes, and so if anyone were broadcasting with the lighthouse method, you'd be unlikely to find them. 


Did the "Wow!" signal come from a particular star or group of stars?

Gray: That's a good question, and the short answer is that there's no way to tell.

Even though the Ohio State radio telescope is really big, it looks at a rather large spot in the sky---a spot shaped like an ellipse that's taller than the moon and about a quarter as wide. In a spot of that size, you have literally millions of stars. I've looked at the photographs for that area of the sky, and there are tons of stars there---no particularly intriguing star that stands out as being a likely source of the signal. Now, several years later I looked for the signal with the Very Large Array in New Mexico. Unlike some of the older telescopes it can give you a pretty good radio image of the sky, because its various telescopes make up one giant antenna that's twenty miles across. And it gives you pretty good resolution, so if you'd seen the "Wow!" with the VLA you really could tell which star a radio signal would have come from. 

  
tasmaniatelescope.jpg
The Mount Pleasant Radio Observatory in Tasmania

 
What was it like working with the Very Large Array in New Mexico? Did you get a thrill out of that? 


Gray: I did. The Very Large Array was, until the end of the twentieth century, the largest radio telescope ever built. It's the same array of antennas featured in the film Contact. It's an unbelievable machine. It can take pictures of the radio sky with the same resolution as an optical telescope, allowing you to see literally millions of objects across the sky. Most of them are distant galaxies with wild things going on at their core...

Getting to use the Very Large Array to look for the 'Wow!" was very unexpected. As far as I can tell, no amateur astronomer had ever done it. Nobody had ever used the full array to look for an extraterrestrial signal at all. It's funny when you show up, they give you a rundown of all the technical stuff, but they also give you a brochure on how to survive rattlesnake bites, because if you go wandering into the desert out there you might get bitten. 

But it's a credit to Big Science that they let me use the Very Large Array to look for the "Wow!" signal. I wouldn't have expected it, and it suggests that Big Science, as an enterprise, isn't quite as ivory tower or exclusive as you might think. 


 You're coming at this as from the field of data analysis, rather than as a professional astronomer, do you think you brought a special skill set to this problem? Were there any insights you had that might not have been as intuitive to an astronomer?


Gray: Well, astronomers generally look at things like stars, things that aren't quite eternal, but that last for a really long time. As a result some astronomers may bring a certain expectation to a radio signal, an expectation that it's going to be there all the time. The people who do SETI, who are often but not always astronomers, have a mindset that it's sensible to look for the really strong signal that is going to be there all of the time.

Because my education is not in astronomy or engineering, it may be that I bring a kind of practicality to this, especially as it concerns the practicality and economics of what it takes to broadcast a signal like that. Broadcasters, just like those of us who are listening, might not be able to command enormous resources, they might not be in charge of whatever political systems are responsible for distributing resources to science in their little corner of the universe. And so as a result they might be forced to use signals that are not present all of the time and therefore those signals may be difficult to find.

The other thing is: Over the years I've talked to a lot of astronomers and a lot of people involved with SETI, and whenever the topic of the "Wow!" comes up, they seem to believe that everybody has looked for it, that it's been checked out. But I've never been able to find anyone else who looked for it. In fact, nobody other than Ohio State seemed all that interested in trying to confirm it at all. Now fortunately that created a situation where I was able to convince several scientists to help me look for it, using various kinds of radio telescopes, including the Very Large Array, the Mount Pleasant Radio Observatory in Tasmania, and the small one that I built myself. So it's possible that what I bring to this is simply the willingness to go out and look.

In a hundred years from now it's likely that we won't be limited to these giant dish things that stare at the sky and only see one little spot. It's possible that there will be some sort of technology that can look at the whole sky at the same time, with the same sensitivity as you get with a big dish, and perhaps, when we look, at some interval we'll see a flash, a signal, and maybe that's the way we'll find broadcasters, if any are out there. But in the meantime, you know, you have to keep a line in the water.


From The Atlantic @ http://www.theatlantic.com/technology/archive/2012/02/the-wow-signal-one-mans-search-for-setis-most-tantalizing-trace-of-alien-life/253093/


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