This is a picture of the stars near the center of our own galaxy, the Milky Way. It is now virtually certain that a black hole with a total mass of 2 million times that of our sun is located at the center of the Milky Way. Astronomers have come to this conclusion by closely following over a long time period the orbits of the stars closest to the galactic center. In one particular case,  using one of the Paranal Observatory's very large telescopes and a sophisticated infrared camera, astronomers patiently followed the orbit of a particular star, designated S2, as it came within about 17 light-hours of the center of the Milky Way (17 light-hours is only about 3 times the radius of Pluto's orbit). This star’s  motion suggested that it was moving in the gravitational field of a supermassive black hole.