Which object has gravity strong enough that light cannot escape its surface?

Which object has gravity strong enough that light cannot escape its surface?

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

Answer: (B)

The object with gravity strong enough that light cannot escape its surface is a black hole. A black hole forms when a massive star exhausts its nuclear fuel and collapses under its own gravitational pull. The gravitational force near a black hole is so intense that it creates a boundary known as the event horizon. Once light crosses this boundary, it cannot reach the outside universe, rendering the black hole invisible and giving it the characteristic of trapping everything, including light, within it.

In contrast, while a neutron star does have incredibly strong gravity, it is not sufficient to prevent light from escaping, and it is observable through radiation emitting from its surface. A white dwarf, although it starts off as a remnant of a star, also has weaker gravity compared to a black hole and can emit light. Similarly, a red giant is a stage in stellar evolution where a star expands, but its gravity is not strong enough to prevent light escape; it can still radiate light. Therefore, only a black hole possesses the unique characteristic of preventing light from escaping due to its extreme gravitational pull.