A recent study led by researchers including Bo-Lun Huang, Zhen-Zhao Tao, and Tong-Jie Zhang has advanced our understanding of waste heat emissions in nearby galaxies. Utilizing data from the Wide-field Infrared Survey Explorer (WISE), the team examined the presence of galaxy-scale (Dysonian) waste heat, specifically in the mid-infrared spectrum.
The research began with data from the 2MASS Redshift Survey (2MRS), which the team cross-matched with CatWISE2020 and AllWISE databases. To ensure accuracy, they applied established mid-infrared active galactic nucleus (AGN) and starburst vetoes, as outlined by notable researchers including Stern and Jarrett. The analysis treated WISE bands W1 and W2 as baseline indicators while using W3 and W4 to establish constraints on waste heat emissions.
For a range of blackbody waste heat temperatures between 150 K and 600 K, the researchers converted W3/W4 photometry into conservative upper limits on bolometric waste heat luminosity. This conversion utilized the WISE bandpass color correction, resulting in median caps of approximately (5-9) x 10^8 L_sun across the examined temperature range.
The study revealed that as the threshold for waste heat increases, the one-sided 95% upper bound on the fraction of nearby galaxies potentially hosting waste heat above that threshold decreases. Notably, this fraction approaches 1/6500 at higher thresholds, constrained by the sample size.
The findings indicate a transition in sensitivity from W4 at around 300 K. Applying the AGENT formalism, the team inferred that a Milky Way-like stellar luminosity of L_ = 3 x 10^10 L_sun would suggest typical per-galaxy caps of approximately 21% of this luminosity could be converted into waste heat at the 300 K mark.
To visualize the interaction of their mid-infrared AGN and starburst rejection with plausible galaxy-scale waste heat spectral energy distributions, the researchers presented a WISE W1−W2 versus W2−W3 color–color diagram. This representation aids in understanding how various galaxies might exhibit waste heat emissions.
This research has been accepted for publication in The Astronomical Journal and is set to contribute significantly to ongoing discussions in the fields of astrobiology and the Search for Extraterrestrial Intelligence (SETI). The findings not only enhance the scientific community’s grasp of galaxy emissions but also set the stage for future inquiries into the thermal signatures of distant galaxies.
The full paper, comprising 18 pages, includes 12 figures and 2 tables, and was submitted on January 12, 2026. For those interested in further details, the research is available on arXiv under the reference arXiv:2601.07297.
