A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars

TL;DR

This study measures the variation of the fine-structure constant, α, using spectra from 17 Sun-like stars, finding no significant variation within 50 parsecs and establishing a precise local reference.

Contribution

The paper provides the first high-precision local measurement of α variation using stellar spectra, reducing systematic effects by selecting solar twins.

Findings

α varies by less than 50 ppb within 50 parsecs

Ensemble measurement achieves 12 ppb precision

No significant variation detected in the local stellar neighborhood

Abstract

The fine structure constant, $\alpha$, sets the strength of the electromagnetic force. The Standard Model of particle physics provides no explanation for its value, which could potentially vary. The wavelengths of stellar absorption lines depend on $\alpha$, but are subject to systematic effects owing to astrophysical processes in stellar atmospheres. We measured precise line wavelengths using 17 stars, selected to have almost identical atmospheric properties to those of the Sun (solar twins), which reduces those systematic effects. We found that $\alpha$ varies by $\lesssim$50 parts-per-billion (ppb) within 50 parsecs from Earth. Combining the results from all 17 stars provides an empirical, local reference for stellar measurements of $\alpha$ with an ensemble precision of 12 ppb.