which description best summarizes the steps that take place during black hole formation, in the correct order

Answer 1

The formation of a black hole typically involves several key steps, particularly in the context of a massive star. Here is a summarized sequence:

1. Stellar Formation: A massive star forms from the gravitational collapse of gas and dust in a nebula.

2. Main Sequence Phase: The star enters the main sequence stage of its lifecycle, where it fuses hydrogen into helium in its core.

3. Expansion to Giant/Supergiant: Once hydrogen in the core is depleted, the core contracts and heats up, leading to the fusion of heavier elements (helium, carbon, oxygen, etc.). The outer layers expand, and the star becomes a red supergiant.

4. Core Collapse: When the star can no longer sustain fusion—usually when iron builds up in the core—fusion ceases because iron fusion does not produce energy. The core collapses under the force of gravity.

5. Supernova Explosion: The collapse of the core triggers a supernova explosion, which blasts the outer layers of the star into space.

6. Black Hole Formation: If the remaining core's mass exceeds the Tolman-Oppenheimer-Volkov limit (approximately 2-3 solar masses), it collapses into a singularity, forming a black hole.

This sequence can vary slightly based on the initial mass of the star and other factors, but this is the general process for the formation of a stellar black hole.