The supermassive black hole at the center of the Milky Way Galaxy, known as Sagittarius A*, has a mass of more than 3.7 million times that of our sun. It is so dense that nothing can escape its gravitational pull, not even light. Therefore, Sagittarius A* cannot be seen directly, but its influence on nearby stars is clearly visible, and provides a signature as to what is happening inside the black hole according to researchers at Northwestern University and UCLA, who are performing the most comprehensive study of Sagittarius A* to date. Their work has provided the best evidence yet that a supermassive black hole does indeed exist at the center of the Milky Way.