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Nearby galaxies in our universe show no signs of advanced alien civilizations — at least for now.
A new study that examined the most promising galaxies we can see out of a collection of 100,000 found no signs of the waste energy that such alien civilizations might generate, showing that they're extremely rare, if not nonexistent. The galaxies were chosen because they emit a large amount of heat, but rather than being the byproduct of alien factories the emissions seem to come from less exotic, natural causes such as buildups of dust.
Earlier this year, a team of astronomers led by Jason Wright, of Pennsylvania State University, studied 100,000 galaxies that NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft could best observe, searching for signs of a civilization capable of harnessing the energy of an entire galaxy.
Wright's team identified 93 sources exhibiting both extreme mid-infrared emission and colors. In the new study, author Michael Garrett investigated those that had been well studied in the past, in an attempt to determine possible sources of the excessive radiation. Garrett is a professor at the University of Leiden and the general and scientific director of ASTRON, the Netherlands Institute for Radio Astronomy.
He found that the majority of the systems created emissions that could be best explained by natural astrophysical processes, such as dust generated and heated by massive star formation. He concluded that advanced civilizations capable of harnessing the power of their galaxies are scarce or nonexistent.
"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," Garrett said in the statement, referring to the Kardashev scale used to rank civilizations' energy use.
"It's not what we would predict from the physical laws that explain so well the rest of the physical universe," Garrett said.
He suggested that such civilizations could be far more energy efficient, producing very little waste heat, beyond scientists' current understanding of physics.
"What's important is to keep on searching for the signatures of extraterrestrial intelligence until we fully understand just what is going on," Garrett said.
The research was detailed Sept. 15 in the journal Astronomy & Astrophysics.
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