what is black hole form?
In google type:
black hole form
A star that died.
http://syzygyastro.hubpages.com/hub/Origin-and-Evolution-of-Black-Holes
A black hole is formed from the remnants of a massive star that has undergone a gravitational collapse. To understand how a black hole forms, let's break it down into steps:
1. Stellar Evolution: A star begins its life as a massive, hot, and dense cloud of gas and dust. Through the process of gravitational contraction, the cloud starts to heat up and ignite nuclear fusion at its core. This fusion process, where hydrogen atoms combine to form helium, produces an outward pressure that balances the inward gravitational force.
2. Fuel Depletion: After burning hydrogen for millions or billions of years, the star exhausts its nuclear fuel. At this point, depending on the star's mass, core temperatures and pressures increase as fusion transitions to heavier elements like helium, carbon, and oxygen. This process continues until the core is made almost entirely of iron.
3. Supernova Explosion: Iron cannot be fused through nuclear reactions, so as the iron core accumulates to a critical mass, it becomes unstable. This instability causes the core to collapse under its own gravity very suddenly. The collapse creates an intense shockwave that propagates outward from the core through the star's layers, resulting in a supernova explosion. The outer layers are expelled into space, while the core collapses further.
4. Formation of a Singularity: The innermost core of the star collapses into an incredibly dense region called a singularity. At the singularity, the laws of physics, as we currently understand them, break down. It is a point of infinite density and spacetime curvature where the mass of the star is compressed to a point of zero volume.
5. Event Horizon: Surrounding the singularity is the event horizon, which is the boundary beyond which nothing, not even light, can escape the gravitational pull of the singularity. The event horizon defines the size of the black hole and is sometimes referred to as the "point of no return." Anything that crosses this boundary is trapped inside the black hole forever.
It's important to note that while we have a good understanding of the theoretical aspects of black holes, direct observation is challenging due to their extreme nature. Scientists mainly study black holes by observing their effects on surrounding matter and spacetime.