The tight mathematical link between the different types of light coming from galaxies is mostly a trick of perspective.
April 25, 2026
Original Paper
Geometry, Not Calorimetry, Drives the Radio/Infrared/Gamma-Ray Correlation
arXiv · 2604.21224
The Takeaway
Astronomers have relied on a correlation between radio, infrared, and gamma-ray emissions to measure how much energy a galaxy is producing. New analysis reveals that this correlation is not caused by the internal physics of cosmic rays as previously believed. Instead, it is a byproduct of the way we view the three-dimensional geometry of galaxies from our position on Earth. This finding suggests that what we thought was a reliable thermometer for the universe is actually an optical illusion of projection. We may need to re-evaluate our understanding of how stars form and evolve across the history of the cosmos.
From the abstract
We investigate whether the observed radio-infrared-$\gamma$-ray correlation in star-forming galaxies is a geometric effect rather than a signature of local cosmic-ray (CR) calorimetry. Using the GALPROP framework, we generate synthetic observations for external viewers from a grid of 3D Milky Way models with varied CR source, gas, interstellar radiation, and magnetic field distributions, all normalised to reproduce local CR data. We find that a tight, quasi-linear correlation arises naturally fr