The mystery of alpha and the isotopes
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
We report unbiased Artificial Intelligence (AI) measurements of the fine structure constant α in two proximate absorption regions
in the spectrum of the quasar HE0515−4414. The data are high resolution, high signal to noise, and laser frequency comb
calibrated, obtained using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO)
spectrograph on the VLT. The high quality of the data and proximity of the regions motivate a differential comparison, exploring
the possibility of spatial variations of fundamental constants, as predicted in some theories. We show that if the magnesium
isotopic relative abundances are terrestrial, the fine structure constants in these two systems differ at the 7σ level. A 3σ
discrepancy between the two measurements persists even for the extreme non-terrestrial case of 100 per cent 24Mg, if shared by
both systems. However, if Mg isotopic abundances take independent values in these two proximate systems, one terrestrial, the
other with no heavy isotopes, both can be reconciled with a terrestrial α, and the discrepancy between the two measurements
falls to 2σ. We cannot rule out other systematics that are unaccounted for in our study that could masquerade as a varying
alpha signal. We discuss varying constant and varying isotope interpretations and resolutions to this conundrum for future high
precision measurements.
in the spectrum of the quasar HE0515−4414. The data are high resolution, high signal to noise, and laser frequency comb
calibrated, obtained using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO)
spectrograph on the VLT. The high quality of the data and proximity of the regions motivate a differential comparison, exploring
the possibility of spatial variations of fundamental constants, as predicted in some theories. We show that if the magnesium
isotopic relative abundances are terrestrial, the fine structure constants in these two systems differ at the 7σ level. A 3σ
discrepancy between the two measurements persists even for the extreme non-terrestrial case of 100 per cent 24Mg, if shared by
both systems. However, if Mg isotopic abundances take independent values in these two proximate systems, one terrestrial, the
other with no heavy isotopes, both can be reconciled with a terrestrial α, and the discrepancy between the two measurements
falls to 2σ. We cannot rule out other systematics that are unaccounted for in our study that could masquerade as a varying
alpha signal. We discuss varying constant and varying isotope interpretations and resolutions to this conundrum for future high
precision measurements.
Date Issued
2025-05-01
Date Acceptance
2025-01-29
Citation
Monthly Notices of the Royal Astronomical Society, 2025, 539 (1), pp.L1-L6
ISSN
0035-8711
Publisher
Oxford University Press
Start Page
L1
End Page
L6
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
539
Issue
1
Copyright Statement
© 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Subjects
ABSORPTION SYSTEM
Astronomical instrumentation, methods and techniques: spectroscopic
Astronomy & Astrophysics
CALIBRATION
CARBON
Cosmology: cosmological parameters, observations
ESPRESSO
FUNDAMENTAL CONSTANTS
Galaxies: quasars: absorption lines
LINE
Physical data and processes: astroparticle physics
Physical Sciences
QUASAR
Science & Technology
STRUCTURE CONSTANT MEASUREMENTS
TIME-VARIATION
VARYING ALPHA
Publication Status
Published
Date Publish Online
2025-01-30