Black holes are formed through the death of massive stars. Stars with more than 8 times the mass of our Sun maintain their structure through a balance of forces. The inward pull of gravity is counteracted by the outward pressure generated by nuclear fusion in the star's core. This balance keeps the star stable throughout most of its life.
As the star ages, it begins to fuse lighter elements into heavier ones. First hydrogen into helium, then helium into carbon, and so on. This process continues, creating layers of different elements within the star. Eventually, the star develops an iron core. This is a critical turning point because iron fusion doesn't produce energy - it actually consumes it. Without energy production to counteract gravity, the star faces an inevitable collapse.
When the iron core forms, the star faces a critical moment. Without the outward pressure from fusion to counterbalance gravity, the core rapidly collapses. This collapse happens incredibly quickly - in less than a second. As the core implodes, the outer layers of the star fall inward but then rebound with tremendous force. This creates a massive explosion known as a supernova, one of the most energetic events in the universe. The supernova blasts away the star's outer layers into space, leaving behind only the collapsed core.
If the remaining core after the supernova is massive enough - typically more than about 3 times the mass of our Sun - a black hole will form. At this critical mass, gravity becomes so intense that it overcomes all other forces in nature, including the pressure that supports neutron stars. The core continues to collapse, theoretically compressing all its mass into an infinitely dense point called a singularity. Surrounding this singularity is the event horizon - a boundary in spacetime beyond which nothing, not even light, can escape. This combination of the singularity and its event horizon is what we call a black hole.
To summarize what we've learned about black hole formation: Black holes form from the gravitational collapse of massive stars at the end of their life cycle. These stars fuse lighter elements into heavier ones until they develop an iron core that cannot produce energy through fusion. Without the outward pressure from fusion to counterbalance gravity, the core rapidly collapses. This collapse often triggers a supernova explosion that ejects the star's outer layers into space. If the remaining core is massive enough - typically more than about 3 times the mass of our Sun - it will continue collapsing to form a black hole with a singularity at its center and an event horizon from which nothing can escape.