West Australian scientists have confirmed little green men were not behind the mysterious, cigar-shaped object spotted in our solar system late last year.
Named Oumuamua, astronomers thought they were looking at a comet or asteroid when the University of Hawaii spotted it in October.
But they soon realised its orbit and long, cylindrical shape meant it was our first known visitor from interstellar space.
Exactly what it is is not known.
The find triggered speculation Oumuamua, which is loosely translated from the Hawaiian as 'a messenger that reaches out from the distant past,' could be an alien spacecraft.
Lead researcher Steven Tingay said the Murchison Widefield Array telescope in remote central WA was used to check for radio transmissions coming from the object between the frequencies of 72 and 102MHz, similar to the frequency range in which FM radio is broadcast.
The telescope is made up of thousands of antennas attached to hundreds of "tiles" that dot the Murchison region, one of the most radio quiet areas on the planet.
"We didn't set out to observe this object with the MWA but because we can see such a large fraction of the sky at once, when something like this happens, we're able to go back through the data and analyse it after the fact," Professor Tingay said.
Although they failed to find signs of intelligent life, the research team from Curtin University's International Centre for Radio Astronomy Research has helped expand the Search for Extra-Terrestrial Intelligence (SETI) from distant stars to objects close to home.
If advanced civilisations do exist elsewhere in our galaxy, they might develop the capability to launch spacecraft over interstellar distances and use radio waves to communicate, Prof Tingay said.
But he said the possibility of such advanced alien life was extremely low.
Researchers speculate there are more than 46 million Oumuamua-like interstellar interlopers cross the solar system every year.
While too far away to study with current technology, future telescopes such as the Square Kilometre Array are set to reveal more about these visitors.
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