- Researchers found seven stars in our galaxy that might host alien megastructures called Dyson spheres.
- But these stars' strange behavior could also be explained by other phenomena, like clouds of dust.
- They'll need much more evidence to confirm that Dyson spheres truly surround these stars.
In the search for intelligent alien life, finding a Dyson sphere would be like hitting the jackpot.
Theoretically, super-advanced alien societies could build these giant, ultra-high-tech megastructures around their host stars to harness solar energy.
Scientists have yet to find proof that Dyson spheres exist. But if they are real, we should be able to spot them, and researchers have been hunting for decades ever since physicist Freeman Dyson first theorized the idea in 1960.
Now, research published in the peer-reviewed journal Monthly Notices of the Royal Astronomical Society has identified seven stars in our galaxy that exhibit some unusual behavior, which the team can't easily explain with natural phenomenon.
What exactly is a Dyson sphere?
Despite what the name suggests, a Dyson sphere isn't necessarily one solid sphere that encases a star, although the most advanced ones could be.
Most likely, "these are satellites with very broad surfaces floating around the star," Suman Majumdar, study co-author and associate professor of astronomy, astrophysics, and space engineering at the Indian Institute of Technology, told Business Insider.
This design would grant an intelligent society access to an unlimited energy source, allowing their population and industry to grow exponentially, according to Dyson's original theory.
The design also means there would be gaps between the satellites where some of the star's radiation could sneak through. And the rest of the light, the satellites would absorb and re-radiate back into space as pulses of infrared radiation known as infrared excess emissions, or IEEs, which could be a way of detecting a distant Dyson sphere from Earth.
For their study, Majumdar and colleagues analyzed more than 5 million stars throughout the Milky Way that exhibit IEEs. But Dyson spheres aren't the only possible explanation.
"There's a lot of reasons that stars might have extra infrared emission. Typically, it's because they're extremely young, and they have a protoplanetary disk," which is a disk of rotating gas and dust around a new star that radiates infrared light, Jason Wright, study co-author and professor of astronomy and astrophysics at Penn State University, told BI.
There are other natural explanations for IEEs, too. That's why the research team had to rule out so many stars from their original list of 5 million Dyson sphere candidates, eventually leaving them with seven that exhibit IEEs they can't easily explain and that could, potentially, host these alien megastructures.
However, future research will need to rule out all other possible explanations first.
Hunting for Dyson spheres
To identify these seven strong Dyson sphere candidates, the researchers used a computer system to sift through a mountain of data collected by Gaia. This European Space Agency satellite is creating a three-dimensional map of more than a billion stars in our galaxy and beyond.
Data from this highly comprehensive survey allowed the research team to select a pool of millions of stars that exhibit IEEs and gradually weed out all the ones that could be explained by natural phenomena.
"It took more than a year to go through this," Majumdar said.
Without Gaia and the massive amount of data it collects, this study wouldn't have been possible.
"I'm really excited for this big data era, like all the big surveys that are coming out — all the things we can learn from this data by looking at it in different ways," Tabetha Boyajian, an associate professor of astrophysics at Louisiana State University who did not work on this study, told BI.
Next, the researchers will look closer at these seven strong Dyson sphere candidates using spectroscopic analysis, Majumdar said. This technique can reveal new information about the radiation these stars emit, and help the researchers rule out other possible explanations for their IEEs.
"It would take a lot of rigor to be able to say confidently that this is not something that nature is doing, it's something that an advanced civilization is doing," Boyajian said.
In the meantime, Gaia continues its survey, populating the database with even more stars for Dyson sphere hunters like Majumdar and Wright, so their search is far from over. In fact, it might just be getting started.
"The same analysis can be actually done on the newer candidates that are populating the catalog," Majumdar said.