The Wow! signal: Alien hunter claims best clue yet to existence of E.T. came from an interstellar lighthouse

An astronomer who has spent three decades hunting for the source of a transmission which is believed by many to be proof of alien life says it may have come from an interstellar 'lighthouse'.

Since 1982, Robert Gray has been on a quest to solve the puzzle of the 'Wow! signal', an enigmatic blip in the read out of a radio telescope - the like of which has never been seen again since.

Mr Gray, who has just published a book about his attempt to rediscover the signal said he believes it could have come from an alien 'lighthouse'.

The 'Wow!' Signal: This is the printout form the Ohio-based radio satellite that received the enigmatic transmission

The 'Wow! signal' was received at 11.16pm on August 15, 1977 - the night before Elvis died - as a radio telescope in Ohio swept its gaze through the constellation of Sagittarius.

It lasted 72 seconds and was earned its name because of the message of disbelief Jerry Ehman, a researcher with the Search for Extra-Terrestrial Intelligence (SETI) programme, scrawled next to the printout recording it.

The characteristics of the signal - a rise and fall in its 'loudness' were exactly what the alien-hunters had been told to look out for.

Eighteen years previously, researchers had put themselves in E.T.'s shoes and tried to work out the best way to attract our attention.

They decided that the most noteworthy signal would be a radio signal at exactly 1,420 MHz. This is the vibration frequency of hydrogen, the most common molecule in the universe.

Everyone agreed that it would be the most widely intelligible way of saying, 'We're here - are you?' When the Wow! Signal came in, its frequency was 1,420 MHz.

But with such a massive area of space to cover, the SETI programme had adopted the strategy of sweeping the sky with their radio receivers, meaning that they could only spend a few seconds looking at each spot.

They worked on the assumption they may find an alien 'beacon' or broadcast that was on all the time, and that all they would have to do is survey the sky to find it.

Searching: Researchers discovered the signal using a radio telescope array, like this one at Jodrell Bank in Cheshire

Mr Gray, an economist by trade, told theatlantic.com that he believes the conventional search for an alien 'beacon' that is always transmitting is misguided.

Such a transmission would require vast amounts of energy to operate, the equivalent of thousands upon thousands of Earth-style power plants.

He said: 'They might use some other cheaper strategy - brief periodic broadcasting, a sweeping lighthouse beam, or other methods.'

He added: '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.'