In this project, we are testing fundamental physics by measuring the strength of electromagnetism across our galaxy in regions of very different dark matter density. 

In the Standard Model of Particle Physics, the strength of electromagnetism, represented by α, is assumed to be the same everywhere in the universe with no dependence on any other quantity. It is a "fundamental constant". But physicists suspect that a unified Theory of Everything exists (a deeper set of physical laws beyond the Standard Model) which explains these fundamental constants, including that they may vary and be intimately connected to the physics behind dark matter and dark energy which dominate our universe. 

Sun-like stars as fundamental physics laboratories 

Our project solves a long-standing problem in attempts to map the strength of electromagnetism across our galaxy for the first time. We will use our Sun as a "reference laboratory" to compare with almost identical "solar twin" stars. The thousands of absorption lines in the spectra of Sun-like stars should shift in a distinct pattern if α varies. But the enormous activities of stellar surfaces also shifts these lines. To separate this stellar astrophysics from possible changes in α, we will compare each line to the same one in the reference laboratory, our Sun. We have already demonstrated that this allows us to measure α with better than one part-per-million precision, a huge advance in this field. 

Distant twins 

We are ready to apply our new approach to solar twin stars across our galaxy, but only very nearby ones are currently known. Our project involves discovering new solar twins in regions of very different dark matter densities across our galaxy with the four-metre Anglo-Australian Telescope in New South Wales. We will then take high-quality spectra of the best twins with the world's best new optical spectrograph ,called ESPRESSO, on the eight-metre Very Large Telescope in Chile.

Future fellowship

Professor Murphy received a Future Fellowship in 2018 from the Australian Research Council to lead this new project, which involves collaborators in Australia and across Europe (Germany, Italy, Portugal) and Chile. While the Fellowship will conclude in 2022, the project will continue beyond that time.

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