There are many ways to scour the stars for intelligent life. You can search for radio signatures whose repetitions suggest intentional design, or examine a planet that orbits its star in a so-called Goldilocks Zone conducive for habitation. One of the wildest (but still hypothetically plausible) scenarios involves what’s known as a Dyson sphere.

What is a Dyson sphere?

Named after physicist Freeman Dyson, the idea hinges on an alien civilization so advanced that they invent a method to directly harness the energy of an entire star. Extraterrestrials could theoretically accomplish this feat in a number of ways, but the simplest approach would likely entail encasing a stellar object with orbital installations that absorb solar radiation, convert it into usable energy, and then re-emit that power back to the Dyson sphere’s engineers.

While Dyson himself once described his original 1960 paper as “a little joke,” he later conceded that the underlying technical details are “correct and uncontroversial.” Despite the joke, many researchers today agree, and argue that searching for Dyson spheres is one of the easiest ways to identify extraterrestrial life.

Enter the Webb

Unfortunately, an ongoing cosmic survey called Project Hephaistos at Sweden’s Uppsala University has once again crossed off multiple candidates from their list of suspects. According to their findings detailed in two soon-to-be published studies, a pair of faint, distant red dwarf stars aren’t surrounded by high-tech alien energy harvesters. Although disappointing, the findings highlight the ongoing versatility of one of astronomy’s most impressive tools—the James Webb Space Telescope (JWST or Webb).

Astronomers theorize that any functioning Dyson sphere will generate a technosignature in the form of waste heat that’s emitted as excess mid-infrared radiation. Researchers including Uppsala University astrophysicist Andreas Korn previously flagged multiple dwarf stars with “unusual infrared properties that seem[ed] to resemble those expected for Dyson spheres.” These were selected while employing the European Space Agency’s Gaia satellite and NASA’s Wide-field Infrared Survey Explorer (WISE), with the candidates exhibiting unexpectedly low optical fluxes and higher infrared fluxes. The subject pool was vast—around 1 million stars located within around 1,000 light-years of Earth.

“This is the signature that we were looking for: a star that is a little bit too faint in the optical and has substantial amounts of waste heat in the infrared,” Korn recently explained.

The team ultimately determined their most promising options were two faint M-dwarf stars that are invisible to the naked eye here on Earth and about a few billion years old each. Researchers then used the JWST to gain a more focused look at each star. Sadly, neither ended up revealing themselves as an elusive Dyson sphere. In actuality, they are pretty standard M dwarfs whose energy is jumbled by background galaxies.

“WISE gives us just a coarse image, and that’s why the photons from the background galaxy and the M dwarfs were blended together so we couldn’t tell them apart,” explained Korn. “But with Webb, we can tell the two apart and conduct separate analyses of either the galaxy or the foreground M dwarf.”

This isn’t the first time Project Hephaistos has encountered similar issues. As time goes on, it appears that many of their Dyson sphere candidates are obscured by background galaxies. That may not always be the case, however. Multiple proposed mid-infrared telescopes—including the Giant Magellan Telescope—are scheduled to arrive by the 2030s. Until then, the hunt for Dyson spheres continues.

 

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