On Thursday, astronomers announced the first observations of the effect of a black hole’s gravitational redshift — light coming from a star in the gravitational field near a black hole looked redder than it would’ve outside the black hole’s influence.
The black hole responsible was Sagittarius A* (pronounced “Sagittarius A-star”), the supermassive black hole at the center of our Milky Way galaxy. Astronomers think that most large galaxies like the Milky Way should have supermassive black holes in their centers, but it wasn’t until the past couple decades that they had compelling evidence that Sgr A* is our supermassive black hole.
The discovery of Sgr A* is credited to two astronomers, Bruce Balick and Robert L. Brown, who published a paper in 1974 describing a bright radio source in a small region at the very center of the Milky Way.
Astronomers had known for a while that there were a ...
