14 April 2015
Search of 100,000 galaxies for advanced civilizations yields no obvious candidates
by Will Parker
Using data from NASA's WISE orbiting observatory, a team of scientists say they have found no evidence of the mid-infrared energy emissions we would expect to observe from other advanced civilizations. The research is a significant expansion of earlier work in this area, which looked at only 100 or so galaxies.
"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 at the Center for Exoplanets and Habitable Worlds at Penn State University. Wright's team's first paper about "Glimpsing Heat from Alien Technologies Survey" will appear in the Astrophysical Journal.
Back in the 1960s, physicist Freeman Dyson proposed that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.
"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 explained. "This same basic physics causes your computer to radiate heat while it is turned on."
The team scoured almost the entire catalog of the WISE satellite's detections - nearly 100 million entries - for objects consistent with galaxies emitting too much mid-infrared radiation. They then examined and categorized around 100,000 of the most promising galaxy images. "We found about 50 galaxies that have unusually high levels of mid-infrared radiation," said Wright. "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."
But whatever the case, Wright said; the team's non-detection of any obvious alien-filled galaxies is an interesting and new scientific result. "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."
Interestingly, among the team's discoveries are some mysterious new phenomena in our own Milky Way galaxy. These include a bright nebula around the nearby star 48 Librae, and a cluster of objects easily detected by WISE in a patch of sky that appears totally black when viewed with telescopes that detect only visible light. "This cluster is probably a group of very young stars forming inside a previously undiscovered molecular cloud, and the 48 Librae nebula apparently is due to a huge cloud of dust around the star, but both deserve much more careful study," said co-investigator Matthew Povich.
"As we look more carefully at the light from these galaxies," added Wright, "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."
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Source: Penn State University