Advanced Civilizations Could be Using Dyson Spheres to Collect Unimaginable Energy From Black Holes

Obviously, no such structure has yet been detected. Still, the paper proves that it is possible to do so, despite no visible light making it past the sphere’s surface and a black hole’s reputation for being light sinks rather than light sources. To understand how we would detect such a system, first, it would be helpful to understand what that system would be designed to do.

The authors study six different energy sources that a potential Dyson sphere could collect around a black hole.  They are the omnipresent Cosmic Microwave Background radiation (which would be washing over the sphere no matter where it was placed), the black hole’s Hawking radiation, its accretion disk, its Bondi accretion, its corona, and its relativistic jets. 

Some of these energy sources are much more high-powered than others, with the energy from the black hole’s accretion disk leading the pack in terms of potential energy captures. Other types of energy would require completely different engineering challenges, such as capturing the kinetic energy of the relativistic jets that shoot out from the black hole’s poles. Size obviously plays a large factor in how much energy these black holes emit. The authors primarily focus on stellar-mass black holes as a good point of comparison against other potential energy sources. At that size, the accretion disk alone would provide hundreds of times the energy output of a main-sequence star.

It would be impossible to build a Dyson sphere around any object that size with current known materials. But the type of civilization that would be interested in taking on such an engineering challenge would most likely have much stronger materials than we do today. Alternatively, they could work with known materials to create a Dyson Swarm or Dyson Bubble, which doesn’t require as much material strength but does lose some of the energy that a complete sphere would capture, and adds multiple layers of complexity when coordinating orbital paths and other factors. Any such structure would have to be outside the accretion disk to get the full benefit from the energy the black hole emits.

Even a single sphere around a single stellar-mass black hole would be enough to push any civilization that created it into Type II territory, giving it a level of power output unimaginable with current technology. But even such a potent civilization most likely won’t be able to bend the laws of physics.  No matter the power level, some of it will be lost to heat.  

To astronomers, heat is simply another form of light – infrared, to be exact.  And according to the researchers, the heat emitted by a Dyson sphere around a black hole should be detectable by our current crop of telescopes, such as the Wide Field Infrared Survey Explorer and the Sloan Digital Sky Survey, to a distance of about 10kpc at least.  That’s about 1/3 of the distance across the entire

Sloan Digital Sky Survey, one of the telescopes that could find a potential Dyson sphere around a black hole. Credit: SDSS Team, Fermilab Visual Media Services