(M. Kornmesser/ESO via AP) This artist's impression provided by the European Southern Observatory in July 2018 shows the path of the star S2 as it passes close to the supermassive black hole at the center of the Milky Way galaxy. As the star gets nearer to the black hole, a very strong gravitational field causes the color of the star to shift slightly to the red, an effect of Einstein's general theory of relativity.