We propose helioseismology as a new, precision probe of fifth forces at astrophysical scales, and apply it on the most general scalar-tensor theories for dark energy, known as degenerate higher-order scalar-tensor theories. We explain how the effect of the fifth force on the solar interior leaves an observable imprint on the acoustic oscillations, and under certain assumptions we numerically compute the nonradial pulsation eigenfrequencies within modified gravity. We illustrate its constraining power by showing that helioseismic observations have the potential to improve constraints on the strength of the fifth force by more than 2 orders of magnitude, as $-1.8\times {10}^{-3}\le Y\le 1.2\times {10}^{-3}$ (at $2\sigma$). This in turn would suggest constraints of similar order for the theory’s free functions around a cosmological background (${\alpha }_H$, ${\beta }_1$).

• Received 24 April 2019
• Revised 12 June 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.091103