Chapter 13, Problem 48A

A black hole is no more massive than the star from which it collapsed. Why then, is gravitation so intense near a black hole?

To determine

To Explain: The intense gravitation near a black hole though it has less mass than the star from which it collapsed.

Explanation of Solution

Introduction:

Black hole is the region in the space where gravity is very strong. The gravity near black hole is so strong so that even electromagnetic radiation such as light cannot escape from it. The origin of the black hole from the collapse of a massive star into itself which causes supernova.

Black holes can be categorized as- miniature, stellar, supermassive and intermediate. Normally, in the star’s core, nuclear fusion processes at the center of the star pushing the star outward; whereas force due to gravity pull it inside. Energy due to fusion process and gravity of the star balance each other. According to the Chandrasekhar’s limit, when the mass of the star is greater than 1.4 times the mass of the sun then star can be converted into the black hole through the process of supernova. After the supernova, there is no outward push force and star core begins to collapse within itself.This process continues and results into high density, high gravity black hole. According to Einstein’s general theory of relativity, gravitational field of these massive black holes can affect the electromagnetic radiation.

Conclusion:

Therefore, star which results into the black hole concentrate its mass in very small region. In small region of black hole,gravity increases tremendously. This is the reason behind intense gravitation near the black hole.