Over the past decades, the black hole has gone from a theoretical construct to the subject of observation. Obviously, it’s impossible to observe an object that traps light itself, but it has been possible to observe some of the matter in its immediate neighborhood and use those observations to make inference about the black hole itself. Although small black holes can form during the death of stars, the most significant black hole anywhere close to the earth is the one at the center of our galaxy—knowing more about its properties can help us explore a variety of issues in cosmology and relativity. Researchers have now tracked a star, called S0-2, though most of its orbit around our galaxy’s black hole, and provide a new estimate for both its mass and distance.
