Colloquium: Michael Murphy (Swinburne, Australia)
Fundamental physics with solar twins
The Standard Model of nature's laws provides no explanation for the fundamental constants, like electromagnetism's strength, alpha. It is therefore up to experiments to test whether fundamental constants are, indeed, constant and universal, or instead vary and depend on other physical parameters. I will describe a new probe of alpha's constancy within our Galaxy, solar twin stars, and show our first results which have an ensemble precision of 12 parts-per-billion. This is already the best astronomical measurement of any fundamental constant so far. The results derive from archival high-resolution optical spectra (HARPS) from the ESO 3.6-m telescope, so there is considerable scope for extending them using larger facilities. Our goal is to map alpha across the Milky Way and, importantly, its widely-varying dark matter density field. This will be a completely new, direct test of physics beyond the Standard Model. I will report our discovery of the most distant solar twins and analogues, up to 4kpc closer to the Galactic Centre, as the first step towards that goal, and outline current and future work.
Nov. 3, 2022, 2:30 p.m. – 3:30 p.m.