Astronomers at the University of Manchester in the U.K. said on September 2, 2020 that they’ve made an analytical breakthrough in the ability to seek and perhaps someday find intelligent extraterrestrial life in our Milky Way galaxy. They said this breakthrough is a “milestone” that could “significantly improve” our chances of finding extraterrestrial intelligence by dramatically expanding the number of stars available for searching. They said their new analytical technique has increased the number of stars that can be analyzed by more than 200 times. And they said they’ve now placed the best limits yet on the prevalence of artificial radio transmitters, dubbed technosignatures, in the Milky Way.
The collaborative research team has been able to dramatically expand the search for extraterrestrial life from approximately 1,400 stars to 280,000, increasing the number of stars analyzed by a factor of more than 200 …
The result suggests that fewer than 0.04% of stellar systems have the potential of hosting advanced civilizations with the equivalent or slightly more advanced radio technology than 21st century humans. As well as improving the limits for nearby stars, the team for the first time has actually placed limits on more distant stars with the caveat that any potential lifeforms inhabiting the outer limits of the galaxy would need even more powerful transmitters in order to be detectable.
The research team consists of University of Manchester masters student Bart Wlodarczyk-Sroka and his advisor Michael Garrett, collaborating with Andrew Siemion, director of the Breakthrough Listen Initiative.
The analysis, say researchers, can only locate intelligent and technically advanced civilizations that use radio waves as a form of communication. They could not, for example, detect “simple” life or non-technical civilizations. They said:
Combing through the catalog produced by the European Space Agency’s (ESA) Gaia spacecraft, which measured the distances to over a billion stars, [we] recalculated limits on the prevalence of transmitters around additional stars within the radio telescope’s fields of view. By selecting stars out to much larger distances (up to about 33,000 light-years) than the original sample of nearby stars, [we] were able to expand the number of stars studied from 1,327 to 288,315.
Team leader Mike Garrett said he’d always been troubled that SETI searches didn’t usually take into account the many other cosmic objects that fall within the range of sky a telescope is sensitive to, in addition to the main target. According to Garrett, the European space Agency’s Gaia spacecraft – which is currently engaged in creating the first-ever three-dimensional map of our Milky Way galaxy – has changed all that. Gaia is gathering a vast quantity of data. Wlodarczyk-Sroka and Garrett have developed a new technique that will enable astronomers to analyze the data more effectively.
In the process, they said, the sheer number of stars studied enabled Wlodarczyk-Sroka to place some of the most stringent limits to date on the prevalence of powerful radio transmitters in this region of our Milky Way galaxy. In addition, for the first time, the team has been able to do this as a function of stellar type. The extended sample includes not only a wide range of main-sequence stars, but also numerous giant stars and white dwarfs. Garrett said:
Knowing the locations and distances to these additional sources greatly improves our ability to constrain the prevalence of extraterrestrial intelligence in our own galaxy and beyond. We expect future SETI surveys to also make good use of this approach.
Our results help to put meaningful limits on the prevalence of transmitters comparable to what we ourselves can build using 21st century technology.
We now know that fewer than one in 1,600 stars closer than about 330 light years host transmitters just a few times more powerful than the strongest radar we have here on Earth. Inhabited worlds with much more powerful transmitters than we can currently produce must be rarer still.
Bottom line: Researchers at University of Manchester have developed a new analytical technique that they say represents “a milestone in SETI.” It will make good use of the data being gathered by ESA’s Gaia satellite and will place limits on what we know about extraterrestrial intelligence in the Milky Way.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.