Milky Way’s giant black hole pinned down: “S2 orbits Sagittarius A* every 15.6 years at a distance of between 17 light hours and five light days. The orbit and estimated mass of the star allow researchers to calculate that the Milky Way’s black hole has a mass 3.7 million times that of our Sun. The black hole’s Schwarzschild radius, equivalent to the ‘size’ of its event horizon, was found to be 11 times the radius of the Sun at 7.7 million kilometres.”