Dr Ragbir Bhathal, a scientist at the University of Western Sydney, picked up the odd signal in December 2008, long before it was announced that the star Gliese 581 has habitable planets in orbit around it.
A member of the Australian chapter of SETI, the organisation that looks for communication from distant planets, Dr Bhathal had been sweeping the skies when he discovered a 'suspicious' signal from an area of the galaxy that holds the newly-discovered Gliese 581g.
The remarkable coincidence adds another layer of mystery to the announcement last night that scientists had discovered another planet in the system: Gliese 581g - the most Earth-like planet ever found.
Dr Bhathal's discovery had come just months before astronomers announced that they had found a similar, slightly less habitable planet around the same star 20 light years away. This planet was called Gliese 581e.
When asked about his discovery at the time Dr Bhathal admitted he had been really excited about what he had possibly stumbled across.
He said: 'Whenever there’s a clear night, I go up to the observatory and do a run on some of the celestial objects. Looking at one of these objects, we found this signal.
'And you know, I got really excited with it. So next I had to analyse it. We have special software to analyse these signals, because when you look at celestial objects through the equipment we have, you also pick up a lot of noise.'
He went on: 'We found this very sharp signal, sort of a laser lookalike thing which is the sort of thing we’re looking for - a very sharp spike. And that is what we found. So that was the excitement about the whole thing.'
For months after his discovery Dr Bhathal scanned the skies for a second signal to see whether it was just a glitch in his instrumentation but his search came to nothing.
But the discovery of Earth-like planets around Gliese 581 - both 581e and 581d, which was in the habitable zone - has also caught the public imagination.
Documentary-maker RDF and social-networking site Bebo used a radio telescope in Ukraine to send a powerful focused beam of information - 500 messages from the public in the form of radiowaves - to Gliese 581.
And the Australian science minister at the time organised 20,000 users of Twitter to send messages towards the distant solar system in the wake of the discoveries.
And Dr Steven Vogt who led the study at the University of California, Santa Cruz, today said that he was '100 per cent sure ' that there was life on the planet.
The planet lies in the star's 'Goldilocks zone' - the region in space where conditions are neither too hot or too cold for liquid water to form oceans, lakes and rivers.
The planet also appears to have an atmosphere, a gravity like our own and could well be capable of life. Researchers say the findings suggest the universe is teeming with world like our own.
'If these are rare, we shouldn't have found one so quickly and so nearby,'
'The number of systems with potentially habitable planets is probably on the order of 10 or 20 per cent, and when you multiply that by the hundreds of billions of stars in the Milky Way, that's a large number. There could be tens of billions of these systems in our galaxy.'
He told Discovery News: 'Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it'.
The planet is so far away, spaceships travelling close to the speed of light would take 20 years to make the journey. If a rocket was one day able to travel at a tenth of the speed of light, it would take 200 years to make the journey.
Planets orbiting distant stars are too small to be seen by telescopes. Instead, astronomers look for tell-tale gravitational wobbles in the stars that show a planet is in orbit.
The findings come from 11 years of observations at the W. M. Keck Observatory in Hawaii.
The planet orbits a small red star called Gliese 581 in the constellation of Libra. The planet, named Glieseg, is 118,000,000,000,000 miles away - so far away that light from its start takes 20 years to reach the Earth.
It takes just 37 days to orbit its sun which means its seasons last for just a few days. One side of the planet always faces its star and basks in perpetual daylight, while the other is in perpetual darkness.
The most suitable place for life or future human colonists would be in the 'grey' zone - the band between darkness and light that circles the planet.
'Any emerging life forms would have a wide range of stable climates to choose from and to evolve around, depending on their longitude,' said Dr Vogt who reports the find in the Astrophysical Journal.
If Gliese 581g has a rocky composition similar to the Earth's, its diameter would be about 1.2 to 1.4 times that of the Earth. It's gravity is likely to be similar - allowing a human astronaut to walk on the surface upright without difficulty."
Good thing we have that alien ambassador now.