What astronomical object, from which nothing, not even light, can escape due to its strong gravity, is defined by an event horizon?

What astronomical object, from which nothing, not even light, can escape due to its strong gravity, is defined by an event horizon?

• A. Neutron star
• B. Quasar
• C. White dwarf
• D. Black hole

Answer: (C)

The key idea is the event horizon, a boundary around a black hole where gravity is so intense that the escape velocity there reaches or exceeds the speed of light. Inside this boundary, nothing can get away, not even light, which is why a black hole is defined by its event horizon. Other objects—like neutron stars and white dwarfs—are extremely dense, but their gravity isn’t strong enough to stop all light from escaping, so they don’t have an event horizon. A quasar is a bright object powered by gas falling into a black hole, but the defining feature—the boundary where nothing can escape—is the black hole itself.

The key idea is the event horizon, a boundary around a black hole where gravity is so intense that the escape velocity there reaches or exceeds the speed of light. Inside this boundary, nothing can get away, not even light, which is why a black hole is defined by its event horizon. Other objects—like neutron stars and white dwarfs—are extremely dense, but their gravity isn’t strong enough to stop all light from escaping, so they don’t have an event horizon. A quasar is a bright object powered by gas falling into a black hole, but the defining feature—the boundary where nothing can escape—is the black hole itself.