These galaxies were found to be emitting ‘unusually high’ levels of radiation - possibly indicating ‘the presence of a highly advanced civilisation.’

Within these galaxies, the researchers said it was possible that an alien race could be harnessing the power of the stars - emitting huge amounts of noticeable heat in the process.

The study was led by Dr Jason Wright from the Center for Exoplanets and Habitable Worlds at Penn State University in Pennsylvania.

The Glimpsing Heat from Alien Technologies Survey (G-Hat), published in the Astrophysical Journal, details how the team thought they might see the infrared signature of a race far more advanced than ours.

‘The idea behind our research is that, if an entire galaxy had been colonised by an advanced spacefaring civilisation, the energy produced by that civilisation's technologies would be detectable in mid-infrared wavelengths,’ said Dr Wright.

The energy used by such a race to be noticeable would have to be huge - likely harnessing the power of a galaxy’s stars.

But Dr Wright said that ‘fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths’.

This would make them noticeable to Nasa's Wise telescope, used in the study.

The researchers picked out 100,000 galaxies of interest, and found that 50 of them were emitting ‘unusually high levels of mid-infrared radiation.’

‘Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization,’ said Dr Wright.

However, talking to MailOnline, Dr Wright noted that the findings were not a sure-fire sign of alien life. The observations could simply be due to natural phenomena, such as dust and star formation.

He said, including the 50 galaxies, none of the 100,000 were found ‘with more than 85 per cent of their light being used by alien industry.’

However, it’s possible that some galaxies do harbour advanced alien life - but they are emitting less energy than we can currently detect.

‘The harder we look and the longer we work, the better our detection limit will be, and the less energy a galaxy-spanning civilization would need to use for us to discover it,’ he added.

Another possibility, of course, is that such civilisations simply don’t exist.

But Dr Wright and his colleagues will be hoping that is not the case - and they are continuing to study galaxies for signs that we are not alone. 

(dailymail.co.uk)