Part 9/13:
Black holes form from the collapse of massive stars that exceed a certain threshold during their death throes, resulting in a gravitational pull so strong that the escape velocity surpasses the speed of light. When this happens, the star’s core compresses into an incredibly small point—sometimes as tiny as a lime—yet containing more mass than Earth.
Scientists infer the existence of black holes indirectly, by observing their effects on nearby matter and the fabric of spacetime. For example, many stars exist in binary systems, where one star’s material spirals onto a companion black hole, emitting X-rays detectable by telescopes. These observations confirm black holes' presence without needing to see them directly.