Century-Old Relativity Experiment Used To Measure A White Dwarf's Mass

"Astronomers have used the sharp vision of NASA’s Hubble Space Telescope to repeat a century-old test of Einstein’s general theory of relativity. The team measured the mass of white dwarf Stein 2051 B, the burned-out remnant of a normal star, by seeing how much it deflects the light from a background star. The gravitational microlensing method data provide a solid estimate of the white dwarf’s mass and yield insights into theories of the structure and composition of the burned-out star."