After being absorbed and used, the energy from a cosmic object would have to be reradiated or else it would build up and eventually melt the Dyson sphere, as Dyson noted in his 1960 paper. This energy would be shifted to longer wavelengths, so a Dyson sphere around a black hole might give off an unexplainable energy signature in the ultraviolet or infrared, the researchers said.
Several instruments, including NASA’s space-based Wide-field Infrared Survey Explorer (WISE) and the Pan-STARRS telescope in Hawaii, have cataloged billions of objects during their detailed surveys of the night sky, Goto said. Should Dyson spheres around black holes actually exist, it’s possible that their telltale signs have already been recorded by such detectors, he added.
The team is now developing algorithms that can search through these databases and hunt for peculiar entities that might indicate Dyson spheres. “If it can really be found, I would feel ecstatic,” Hsiao said.
Such a search might be useful no matter what it uncovers, Macy Huston, a doctoral candidate in astronomy at The Pennsylvania State University who was not involved in the work, told Live Science. “Even if you’re not finding Dyson spheres, you’re probably going to find something interesting along the way,” they said.
Yet black holes provide distinct challenges to alien mega-engineers. The gravitational monsters tend to be less stable than stars in terms of their energy production, Huston said.
Whereas sunshine glows continuously, black holes often have bursts of activity followed by periods of quiet as they consume larger and smaller amounts of matter in their disks. An alien species might have to watch out for particularly large bursts that could destroy orbiting structures, Huston said.
But “if a species is looking for something more powerful than a star, this could be it,” they said.