Scientists searched 100,000 galaxies for signs of intelligent alien life, but couldn't find any proof that we are not alone in the universe.
The study was conducted using observations from NASA's WISE orbiting observatory, Penn State reported.
"The idea behind our research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization's technologies would be detectable in mid-infrared wavelengths -- exactly the radiation that the WISE satellite was designed to detect for other astronomical purposes," said Jason T. Wright, an assistant professor of astronomy and astrophysics at the Center for Exoplanets and Habitable Worlds at Penn State University.
The findings were published in the Astrophysical Journal Supplement Series on April 15, 2015 in the team's first paper about its Glimpsing Heat from Alien Technologies Survey (G-HAT).
"Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy's stars to power computers, space flight, communication, or something we can't yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths," Wright said. "This same basic physics causes your computer to radiate heat while it is turned on."
The scientists took on the painstaking task of reviewing almost the entire catalogue of WISE satellite's detections, which consists of nearly 100 million entries. They then picked out 100,000 of the most promising galaxy images. Fifty galaxies proved to have high levels of mid-infrared radiation, which could still hold promise for the detection of intelligent alien life.
"Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes. That's interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don't exist, or they don't yet use enough energy for us to recognize them," Wright said.
Despite its failure to find alien life, the study did reveal some never-before-seen phenomena present in the Milky Way. Among these discoveries was a bright nebula surrounding a nearby star, and a cluster of objects that appear black when looked at through a telescope that captures only visible light. This cluster is most likely a group of baby stars forming inside of a molecular cloud.
"As we look more carefully at the light from these galaxies we should be able to push our sensitivity to alien technology down to much lower levels, and to better distinguish heat resulting from natural astronomical sources from heat produced by advanced technologies. This pilot study is just the beginning," Wright concluded.
