A star in which light cannot escape because of the immense gravitational pull at its surface is called a black hole.

Here's why:

* Gravity: Black holes have incredibly dense matter packed into a tiny space. This extreme density creates a powerful gravitational pull.

* Escape Velocity: The escape velocity is the speed an object needs to escape the gravitational pull of a celestial body. For a black hole, the escape velocity exceeds the speed of light.

* Event Horizon: The boundary around a black hole where the escape velocity reaches the speed of light is called the event horizon. Nothing, not even light, can escape from within the event horizon.

Let me know if you have any other questions!