A survey of five million distant solar systems, aided by 'neural network' algorithms, has discovered 60 stars that appear to be surrounded by giant alien power plants.

Seven of the stars — so-called M-dwarf stars that range between 60 percent and 8 percent the size of our sun — were recorded giving off unexpectedly high infrared 'heat signatures,' according to the astronomers.

Natural, and better understood, outer space 'phenomena,' as they report in their new study, 'cannot easily account for the observed infrared excess emission.'

Ever since theoretical physicist Freeman Dyson first proposed the idea at Princeton in 1960, astrophysicists have speculated that advanced extraterrestrials might have constructed massive solar energy collectors around one star or more.

While powering their spacefaring ET civilizations, these hypothetical 'Dyson spheres,' would reveal themselves by radiating more heat than usual, the physicist argued.

Astrophysicists and planetary scientists call 'Dyson spheres' and other concepts like them 'technosignatures,' or simply signs of technology out there in the universe. 

Technosignatures can range from these incredible feats of engineering to more humbling signs, like technologically made pollution — including nitrogen dioxide gas from combustion exhaust or the chlorofluorocarbons (CFCs) that once threatened Earth's ozone layer years ago, both detectable via telescopes light-years away. 

Two teams of astronomers, led by Matías Suazo at Uppsala University in Sweden and Gaby Contardo at the International School for Advanced Studies in Italy, ran the latest hunt for the tell-tale infrared data that might reveal a distant 'Dyson sphere.' 

The researchers merged data from the European Space Agency's Gaia satellite, the Wide-field Infrared Survey Explorer (WISE) space telescope and the ground-based infrared telescope survey MASS2.

While there may be other explanations for the excess infrared signatures they found, Suazo noted, 'The most fascinating explanation could be actual Dyson spheres.'

Suazo's group in Sweden determined that seven, red M-dwarf stars, each no farther than 900 light-years from Earth, appeared to be producing as much as 60 times more infrared heat than would be expected based on their size. 

For each red dwarf star, they calculated how much of its radiation would have to be blocked off by some possible energy-collecting tech in order to produce the measured ratio of infrared heat vs. visible light.

The values ranged from 3 percent to 16 percent coverage for the seven unusual stars they identified.

'This isn't like a single solid shell around the star,' as one member of Suazo's team, astrophysicist Jason Wright at Pennsylvania State University, told New Scientist.

If these stars proved to be surround by alien power plants, in other words, they'd likely be a variant on the all-encompassing Dyson sphere dubbed a 'Dyson swarm.' 

Such a swarm could come in the form of a large fleet of satellites, which would orbit these stars as a means of collecting energy.

'Additional analyses are definitely necessary to unveil the true nature of these sources,' the team wrote in their study, published this month in the Monthly Notices of the Royal Astronomical Society.