Overview
In the search for technosignatures, astronomers increasingly turn to Dysonian methods—looking for evidence of galaxy-scale engineering that radiates heat at mid-infrared (MIR) wavelengths. Using data from the Wide-field Infrared Survey Explorer (WISE) and the CatWISE catalog, researchers cross-match large galaxy samples with mid-IR measurements to identify anomalous heat signatures that could indicate megastructures such as Dyson spheres. Here we summarize a contemporary approach that starts from the 2MASS Redshift Survey (2MRS) and follows up with CatWISE2020 and AllWISE, applying standard MIR AGN/starburst vetoes to constrain or reveal dysonian waste heat.
Methodology: Building a Clean MIR Sample
The analysis begins with the 2MRS, a comprehensive galaxy redshift survey, which provides the large-scale structure and distances necessary to translate observed MIR flux into intrinsic properties. The 2MRS galaxies are then cross-matched with CatWISE2020 and AllWISE, leveraging multi-epoch photometry that improves sensitivity to faint MIR signals and helps mitigate artifacts common in single-epoch surveys.
To avoid confusion with ordinary astrophysical sources that emit strongly in the MIR, the study adopts a suite of well-established AGN/starburst vetoes. These include:
- Stern et al. (W1-W2 color cut) to separate AGN-like MIR colors from stellar and star-forming galaxies;
- Assef et al. R90 (W1-W2 vs W2) criteria to identify AGN-dominated systems and set robust flux-based thresholds;
- Jarrett et al. color–color diagnostics that map typical galaxy tracks in MIR color space for a clean separation of activity types.
By applying these vetoes, researchers aim to minimize contamination from ordinary star formation and active galactic nuclei (which can mimic unusual waste-heat signatures) while preserving any unusual, diffuse MIR excess potentially associated with Dyson-waste heat. The combination of 2MRS redshifts, CatWISE2020 photometry, and AllWISE measurements creates a scalable pipeline for sifting through tens of thousands of galaxies into a digestible subset for deeper follow-up.
Interpreting Mid-IR Signatures
MID-IR emission in galaxies typically arises from dust grains heated by starlight, star-forming regions, or accretion onto central black holes. A genuine dysonian waste signature would manifest as a diffuse, elevated MIR output that cannot be easily reconciled with conventional astrophysical sources. However, distinguishing between exotic megastructures and natural processes is nontrivial. The veto framework helps, but robust interpretation often requires complementary data and careful modeling of the galaxy’s stellar population and dust content.
Key questions include: Is there a perceptible excess in WISE bands that remains after accounting for redshift, distance, and dust extinction? Does the MIR morphology align with diffuse, galaxy-wide heating rather than compact, nuclear activity? How do the results compare with expectations from natural dust heating versus hypothetical engineered waste heat?
Current Constraints and Implications
Initial results from such cross-matched catalogs typically yield strong constraints on the prevalence of high-temperature or anomalous diffuse MIR emitters within the local universe. A lack of statistically significant excess after applying MIR vetoes suggests that, within the surveyed volume and sensitivity, there is no compelling evidence for galaxy-scale technosignatures of the Dyson sphere variety. This, in turn, narrows the parameter space where dysonian waste heat could exist undetected, or indicates that any such engineering would either be rarer, cooler, or more geometrically complex than simple, isotropic MIR signatures would imply.
Moreover, the methodological framework itself advances the field by providing a transparent, reproducible pathway to scrutinize infrared data for megastructure indicators. Even null results inform theoretical models of extraterrestrial technology, helping to refine expectations for how advanced civilizations might manage energy at galactic scales without triggering obvious MIR signatures detectable with all-sky surveys.
Future Prospects
As infrared surveys extend in depth and resolution, and as CatWISE continues to mature with improved photometry and deblending, the prospects for detecting subtle dysonian waste signatures improve. Integrating ancillary data—such as far-infrared, radio, or optical variability—could sharpen the ability to separate engineered heat from natural processes. In the meantime, the WISE/CatWISE approach provides a rigorous, scalable framework to test one of the most intriguing ideas in the search for extraterrestrial intelligence: that civilizations might leave galaxy-wide thermodynamic footprints in the mid-infrared.
