Original title: Constraints on mu-variations from the methanol CH3OH thermal lines in the Galaxy at galactocentric distances of 1.5 < D_GC < 13 kpc
A. I. Shtein, J. S. Vorotyntseva, S. A. Levshakov · September 2026
Scientists wonder if the fundamental rules of physics stay the same everywhere in space. In this study, researchers checked whether mu, the mass ratio of an electron to a proton, changes across our galaxy. They looked at light emitted by molecules of methanol, a type of alcohol, drifting in space. These molecules produce specific signals, called thermal emission lines, in the 216-220 GHz frequency range. Because these signals shift if the particle mass ratio changes, researchers can test if the constant holds steady. The team studied these signals from seven massive clouds across the galaxy. They found no statistically significant shift in mu. As far as these measurements can tell, this fundamental physical constant remains steady across vast cosmic distances.
Imagine checking if all the thermometers in different parts of a city read the same temperature for boiling water. Each thermometer might be slightly off, but if they all give nearly identical readings, you conclude the boiling point hasn't changed. In this paper, methanol molecules act like thermometers, their light spectra are the temperature readings, and comparing them across the galaxy checks if a fundamental constant has varied.
The electron-to-proton mass ratio is a fundamental constant that affects chemistry and physics. If it varied, it could mean the laws of nature aren't the same everywhere. This study confirms it's stable across our galaxy, reinforcing the uniformity of physical laws.
The abstract does not specify if the study covers all regions of the galaxy or other molecules. It is limited to methanol lines in the 216-220 GHz range and seven specific clouds. The constraints are consistent with previous limits but do not establish variation beyond the tested parameters.
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Constraints on mu-variations from the methanol CH3OH thermal lines in the Galaxy at galactocentric distances of 1.5 < D_GC < 13 kpc — A. I. Shtein, J. S. Vorotyntseva, S. A. Levshakov
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.