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After nearly 40 years, the ‘WOW’ signal still remains a mystery: an alien transmission?

In 1977, a researcher at the SETI spotted a short burst of radio waves lasting 72 seconds, thirty times stronger than the background noise and never be heard again, despite repeated subsequent searches. What was it?

From the moment it began its activities, the program saw SETI astronomers committed to scour the length and breadth of the starry sky, in the hope of receiving some radio signal generated artificially by some alien civilization. Over the years are many false alarms, but also some very interesting short signals, in a fleeting appearances were detected on instruments: if a radio transmission is not repeated, so that it can be studied more carefully, then it is practically impossible to determine whether it is really of natural origin. One of these signals, the most tantalizing of all, is August 15, 1977 was detected, which became famous under the name of ‘Signal WOW’. The transmission was intercepted by astronomer Jerry Ehman while engaged in the use of the Big Ear Radio Observatory, at Ohio State University, in a study project on behalf of SETI. The signal was considered so remarkable that Ehman circled with red pen the shortcut number of printouts printed by computer, noting in the margin the word ‘WOW’, buckling inadvertently the name that later would make famous the signal. The scientists believed that the signal would fit very well to some criteria that allowed to hypothesize an extraterrestrial origin. But, despite many of these working hours, no source was identified, nor was once again possible to intercept the transmission. To date, the ‘WOW’ signal is still a complete mystery. The only certainty of the astronomers is that the signal originated in deep space, so either it is an astrophysical phenomenon still unknown to scientists, or we are dealing with a signal generated by an alien intelligence. But why ‘WOW’ it is so interesting? First, it seems to be an artificial radio signal, rather than a natural emission of radio waves, such as that produced by a pulsar or quasar: the Big Ear radio telescope used a radio receiver with 50 channels, but ‘WOW’ was heard on a single frequency, with no other noise detected on other channels. The natural radio emissions, in fact, very electrostatic noise cause that tends to appear on all frequencies. The signal, however, was “narrow and concentrated,” as you would expect from an artificial signal. Failing to capture for the second time the signal, Ehman excluded the extraterrestrial origin of the signal, by holding that the facts suggested that the signal had departed from Earth and then simply reflected by a debris orbiting junk.

But when they tried to investigate this hypothesis, the scientists got more problems than solutions. The investigation established that it was impossible that the signal was originated from the Earth, and it was equally unlikely that it had been reflected by a piece of space junk. It was too specific signal and these explanations needed too many unprovable assumptions. One of the key issues was the frequency of the signal ‘WOW’ equal to 1420 MHz, one ‘protected spectrum’ in which it is prohibited to transmit to Earth, as used in radio astronomy. The frequency to 1420 MHz, also known as the ‘Line of Hydrogen’. It is in fact normally emitted by hydrogen atoms present in interstellar space. E ‘can detect it evenly in every direction of the universe, and is used for the tracing of our galaxy. But in the SETI program it has another use. Hydrogen is the simplest and most abundant element in the universe and every possible intelligent civilization would be aware of its frequency in space. As a result, researchers at the SETI logical to consider that it is used for any alien broadcasts intended to be heard. It ‘just as logical that astronomers of other civilizations may think the same thing.

Of course, it is also possible that any alien civilizations do not use radio frequencies to communicate, especially if you are more advanced than us. A new branch of SETI, in fact, is now looking for artificial light sources, such as laser beams used as headlights.

As for ‘WOW’, the mystery remains to identify the origin. Though the source is detected somewhere in the constellation Sagittarius, apart from a handful of nearby stars, it is impossible to determine exactly where it originated the signal.

Unfortunately, there is no way for us to know what exactly has caused ‘WOW’, which, even today, you can not explain it properly. Maybe one day you will be able to pick it up again, or a similar signal, and be able to finally solve the mystery. Until then, the 1977 signal will remain a curiosity, a tantalizing hint about the shape that could have an intelligent extraterrestrial signal.



To open the video click on the image, good view from your Alessandro Brizzi.