Such incredibly compact objects cause infinite curvature in the fabric of spacetime. Everything that falls into a black hole is sucked toward the singularity. At some distance away from the singularity, the escape velocity exceeds the speed of light, sometimes dramatically dubbed “the point of no return,” although the technical term is Schwarzschild radius or event horizon. Different types of black holes have very different masses. Stellar-mass black holes are typically in the range of 10 to 100 solar masses, while the supermassive black holes at the centers of galaxies can be millions or billions of solar masses. The supermassive black hole at the center of the Milky Way, Sagittarius A*, is 4.3 million solar masses. This is the only black hole whose mass has been measured directly by observing the full orbit of a circling star. Black holes grow by accreting surrounding matter and by merging with other black holes.