Hongsheng Zhao an in astronomer. He is an expert in topics ranging from stellar dynamical tests of gravity theories to models of dark matter annihilation near the central black hole of the Milky Way. After working as postdocs in Max-Planck, Leiden and Cambridge, he is tenured in University of St Andrews. Since then, he has been awarded Dutch NWO-visitorship at Leiden 2009, several visiting professorships 2005-2019 in Beijing Observatory, Copenhagen Dark Cosmology Center, Charles University in Prague, and Princeton University, Institute of Advanced Study. He is presently on a mid-term visiting professorship at Kavli Institute of Cosmology in Cambridge.
Zhao’s Chaire Gutenberg project is on testing the validity of Newton’s gravity between stars, especially between a pair of stars separated by more than 10,000 earth-sun distance, a previously untested regime. Fortunately the Gaia satellite mission have found many thousand such widely-separated stars. Their observed relative motion allows us to check if Newton’s predictions are correct statistically. If there is an excess of gravity, one could possibly explain the missing matter problem in Galaxies, ie. we see an excess of gravity within our Galaxy, but we still have not detected directly the dark matter. This has huge implications on fundamental physics. Zhao uses Gaia data to check if Newton’s gravity is modified within the Galaxy.
See reference , Banik I. & Zhao H., 2018, MNRAS, 35, 8711, Testing Gravity with Wide Binary stars like α Centauri.