One of the largest-ever searches for distant alien empires has scoured 100,000 galaxies for signs of suspicious infrared activity and found… nothing.
The study by Penn State used data from Nasa’s Wise (“Wide-field Infrared Survey Explorer“) orbiting observatory to scour far-off galaxies for radiation which, astronomers theorise, would likely be produced if a civilisation were powerful enough to colonise thousands of stars.
The theory that aliens might be visible on a galactic scale is based on the ideas of physicist Freeman Dyson, who suggested in the 1960s that galactic civilisations would almost by definition use most of the starlight in their galaxy for their own ends. This should be detectable using mid-infrared telescopes. That wasn’t possible when Dyson’s theory emerged, but Nasa’s Wise telescope does have the ability to make close measurements for thousands of galaxies, and so allow scientists to study the data for telltale signs of life.
No, they didn’t find it. But scientists have found 50 galaxies with unusual radiation signatures, indicating something strange is happening inside many distant collections of stars — even if it’s nothing to do with aliens at all.
Jason T. Wright, who is an assistant professor of astronomy and astrophysics at the Centre for Exoplanets and Habitable Worlds at Penn State University, believes that the sort of tech required by such a monumentally successful species would be visible at extreme distances across the universe. He initiated the new research, known as the Glimpsing Heat from Alien Technologies Survey (G-HAT), to test the theory.
“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 –exactly the radiation that the WISE satellite was designed to detect for other astronomical purposes,” said Wright in a press release. “Whether an advanced spacefaring civilisation 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.”
The study will be published on 15 April in the Astrophysical Journal, and while it hasn’t found clear evidence of space-faring aliens, there are some new phenomena that deserve further work. In particular lead author Roger Griffith identified 50 galaxies out of the 100 million catalogued by Wise, and the 100,000 studied in more detail, which had “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 civilisation,” Griffith said.
It’s been a dampening week for hopes of finding advanced alien life all around; another study, into Fast Radio Bursts in deep space and the possibility they might be a form of hyper-advanced communication, has also turned in a negative result. But in the case of G-HAT, even the failure itself is interesting, Wright claims. “These galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilisations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognise them,” he said.
The study also turned up some interesting new phenomena within our own galaxy, including a bright nebula around the star 48 Librae, and a cluster of objects that appear “totally black” in visible light. The latter is thought to be a group of young stars, while the nebula is probably a dust cloud — but but were unexpected. Meanwhile the search for alien civilisations will continue. “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,” Wright said. “This pilot study is just the beginning.”