A study looking for signs of intelligent alien life in a handful of galaxies has come up short. It means that super-advanced civilizations in our local universe are extremely rare, or absent altogether.
The study, published in the journal Astronomy & Astrophysics, by Professor Michael Garrett from the Netherlands Institute for Radio Astronomy (ASTRON) and Leiden University was a follow-up to another earlier this year that examined 100,000 galaxies. This former study, by a team from Penn State University, was looking for mid-infrared radiation that would be synonymous with an advanced alien race.
It’s thought that a species far beyond our capabilities could utilize entire stars for energy, perhaps surrounding them in structures known as Dyson spheres, producing noticeable mid-infrared radiation. However, almost none of those 100,000 galaxies had any unusual emissions. The astronomers were only able to identify a few hundred that looked slightly promising.
In his research, Garrett investigated some of these galaxies further and found that all of the emissions could be explained by natural astrophysical processes, such as super-heated dust in regions of massive star formation. However, he noted that some of the galaxies still needed to be studied in greater detail.
“Some of these systems definitely demand further investigation but those already studied in detail turn out to have a natural astrophysical explanation,” he said in a statement. “It's very likely that the remaining systems also fall into this category but of course it's worth checking just in case!”
This false-color image shows mid-infrared emissions from the Andromeda galaxy. NASA/JPL-Caltech/WISE Team.
Intelligent civilizations in the universe, if they exist, are thought to progress along a three-step scale, known as the Kardashev scale. Kardashev Type I civilizations would be capable of harnessing the entire power of a planet; currently, humanity is about three-quarters of the way towards this goal. Type II civilizations would utilize the entire power of stars, via aforementioned Dyson spheres, while Type III civilizations would use the power of entire galaxies. If there were any Type III civilizations in our local universe, it’s likely we would notice them.
“The original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don't exist in the local universe,” said Garrett in the statement. “In my view, it means we can all sleep safely in our beds tonight – an alien invasion doesn't seem at all likely!”
It’s not all good news, though. Considering how young Earth is, and that there should be billions of Earth-like planets in our local universe, it’s surprising we haven’t found any other life yet. This problem, known as the Fermi Paradox, has astronomers stumped; where is everyone else?
“Perhaps advanced civilizations are so energy efficient that they produce very low waste heat emission products – our current understanding of physics makes that a difficult thing to do,” said Garrett. “What's important is to keep on searching for the signatures of extra-terrestrial intelligence until we fully understand just what is going on.”