Upper limits on the prevalence of Dyson spheres in the Milky Way

Dyson spheres are hypothetical structures that high-level civilizations may have built up to harvest the energy of their host star. As in any thermodynamic process, the conversion of stellar energy would involve the emission of waste heat that would be emitted as infrared radiation. If we picture a Dyson sphere as a swarm of smaller satellites collecting the energy from its host star, a broad family of partial Dyson spheres with different covering factors seems plausible. At the same time, these partial Dyson spheres would block some of their host stellar light, leading to a drop in their optical fluxes. Nowadays, we count on missions that have mapped the sky in the optical as well as in the mid-infrared, specifically Gaia and WISE. Both together provide magnitude measurements for roughly 10^7 - 10^8 stars in the galaxy and can recover the two signatures mentioned above. Using this data we estimate how many stars are compatible with Dyson spheres based on Dyson sphere models with temperature ranges between 100-1000 K. In this work, we identify four different scenarios: transparent Dyson spheres, Cool Dyson spheres, intermediate states, and perfect cases.