In other news, we have confirmation that even under relativistic conditions, objects of different masses will still fall at the same rate under the same force of gravity. We’ve all seen the experiments where people drop things like a feather and a brick in a vacuum and they both fall the same way. That experiment is hard, but doable here on Earth. Testing things under relativistic conditions, however, required finding a triple star system of truly massive proportions. The system, PSR J0337+1715, contains a neutron star that is a pulsar and two white dwarf stars of two different masses. The 366 beats-per-second rotation of the pulsar gets shifted by the gravitational pull of the two white dwarfs and allows direct measurement of how they are falling around the pulsar. After making a whole lot of measurements, it was clear both objects fall the exact same way, showing once again that Einstein got it right when he figured out relativity.
Max Planck Institute for Radio Astronomy (MPIfR) press release
“An Improved Test of the Strong Equivalence Principle with the Pulsar in a Triple Star System,” G. Voisin et al., 2020 June 10, Astronomy & Astrophysics (Preprint on arxiv.org)