Black Hole Definition

Summary

A black hole is an extremely compact astronomical object whose gravitational field prevents anything, including light, from escaping once it crosses the event horizon. In general relativity, black holes form when enough mass is compressed into a sufficiently small region, causing spacetime to curve extremely strongly. The theory predicts an event horizon surrounding the black hole and, classically, a central singularity where spacetime curvature becomes infinite. Black holes are not directly visible, but their presence can be inferred from their effects on surrounding matter, light, and spacetime. They may form when massive stars collapse, grow by absorbing matter or merging with other black holes, and range from stellar-mass objects to supermassive black holes at the centers of galaxies. Their properties are described primarily by mass, electric charge, and angular momentum.

Key Points

• 1

  A black hole is a region of spacetime from which no object or information-carrying signal can escape.

• 2

  The boundary beyond which escape is impossible is called the event horizon.

• 3

  Black holes are predicted by Einstein's general theory of relativity and can form through the gravitational collapse of massive stars.

• 4

  Their existence is detected indirectly through effects such as accretion-disk radiation, stellar orbits, gravitational lensing, and gravitational waves.

• 5

  A stable black hole is characterized by three main physical properties: mass, electric charge, and angular momentum.