Astronomers searching for laser signals have found no evidence that an extraterrestrial civilisation built a massive structure around the star KIC 8462852, according to Search for Extra Terrestrial Intelligence (SETI) International.
The star KIC 8462852 baffled scientists by displaying large and irregular dips in brightness, far greater than is normally seen from stars orbited by planets.
Even a planet the size of Jupiter would only cause dimming of approximately 1 per cent, but KIC 8462852 was seen to dim by up to 22 per cent, SETI International said in a press release.
The dimming also followed an unpredictable pattern, meaning it could not be caused by a single planet or object orbiting the star.
Jason Wright from Penn State University published a paper suggesting that the light patterns could be caused by an alien megastructure.
“Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build,” Professor Wright told The Atlantic in October.
One of the popular explanations, a Dyson sphere, is shown in an illustration provided by SETI International.
Dyson spheres, originally proposed by science fiction writer Olaf Stapledon in 1937, would surround a star to capture most or all of its energy output.
The idea was named after theoretical physicist Freeman Dyson after he suggested in 1950 that the infrared output of stars could be examined as a way of finding alien civilisations.
Mr Dyson thinks a cloud of objects surrounding a star is more likely than a single structure, and wishes that Dyson spheres had not been named after him.
Megastructure theory ‘rapidly crumbling apart’
In late November, researchers from Iowa State University published a paper arguing that the most likely explanation is a cloud of comet debris on an unusual orbit.
At the time, lead researcher Associate Professor Massimo Marengo said the idea of an alien megastructure could not be discounted.
The SETI research looked directly for evidence of deliberate attempts at communication using laser pulses aimed at the Earth.
Over six nights between October 29 and November 28, scientists at the Boquete Optical SETI Observatory in Panama searched for laser pulses as brief as a billionth of a second.
The Boquete observatory examined all light collected by the telescope for pulses that repeat in a regular, periodic manner, which is an unmistakable signature of an artificial signal, SETI International says.
On three of those six nights, the Allen Telescope Array in northern California scanned KIC 8462852 for narrowband radio signals.
Neither observatory found any signals that were likely to be artificial.
The alien megastructure theory is “rapidly crumbling apart”, admits SETI International president Douglas Vakoch.
“We found no evidence of an advanced civilization beaming intentional laser signals toward Earth.”
SETI International have submitted a paper to The Astrophysical Journal Letters.