Peering into the Heart of Darkness

27,000 light-years away from Earth in the constellation of Sagittarius lies a star called S2. It has an eccentric, high-elliptical orbit around a superdense object that happens to be right in the hot, violent centre of the Milky Way, with the entire spiral galaxy rotating around it. Astronomers have determined that this object is a supermassive black hole, which they call Sagittarius A*, or Sgr A* for short. It’s estimated to be 4.31 million times more massive than our Sun and 15.4 million kilometres wide—and it’s spinning so fast that it travels at 30% of the speed of light. Black holes usually radiate a lot of energy as they guzzle down matter, but ours is strangely quiet at the moment, and astronomers suggest that it is “starved” of matter, and used to be much more active. Although the black hole should be too massive and violent to allow any stars to form near it, observations have shown a cluster of at least 27 young stars orbiting the Sgr A*, called the S-stars. These must have formed further away but were drawn in by Sgr A*’s gravitational pull. The cluster, which includes S2, is currently under half a light-year from the black hole and is slowly being dragged closer with every orbit—and one day, they’ll be swallowed by darkness.

(Image Credit: Chandra X-Ray Observatory)