What Are Black Holes?

Black holes are areas of gravity that are so large that no matter or radiation traveling through space can escape. In fact, black holes are dead stars; because when a large star runs out of fuel, it collapses on itself and forms a black hole.

How Are Black Holes Formed?

You can think of a star as a huge thermonuclear reactor. The fuel of this reactor is continuous fusion reactions in the star's core. In this type of reaction, elements with a smaller atomic number, such as hydrogen, boil together to become elements with a larger atomic number, such as helium. During this fusion, plenty of energy is scattered around. This energy pushes the atoms inside the star outwards.

However, there is another force that causes atoms to scatter so that the star does not scatter: gravity. The inward gravitational force between the atoms balances the outward force of this fusion reaction. Thus, the star remains in a so-called hydrostatic equilibrium.

Although gravity is not an exhaustive phenomenon (to our knowledge), the fusion reaction is not infinite. Stars are formed in the cloud of gas and dust that precedes them (nebulae). Nebulae are clouds of gas and dust scattered around by stars that have already completed their lives. This cloud of gas and dust contains a certain amount of hydrogen atoms; the number of these atoms is not infinite. Therefore, the amount of hydrogen that a star formed in a nebula can consume is also limited. After a while, the star consumes hydrogen fuels. Thus, the fusion reaction gradually slows down; however, the effect of gravity does not change. As the gravity becomes heavy, the hydrostatic equilibrium begins to deteriorate and the star begins to collapse into itself.

As the heavy elements that make up the body of the star begin to collapse inwards, the electrons around the atoms approach each other very much and the effect of other basic physical forces emerges: these atoms begin to repel each other. At one point, this propulsion is far superior to gravity, and the star explodes with great force! This phenomenon is called supernova and even older ones are called hypernova. In the meantime, plenty of energy and atoms are scattered around. As these atoms scatter into space, new nebulae form. These nebulae are like maternity homes that give birth to brand new stars under the effect of gravity.

But the matter remains from the exploding star, trapped inside the nucleus. They sometimes form stars in a different class. However, if the mass of the star collapsing on itself is above a certain limit, celestial bodies of incredible density, such as black holes, are formed. These large masses bend the space-time tissue that makes up the Universe much more than normal masses. You can visualize this by imagining what happens when you drop a 500-kilogram ball on a stretched sheet. The bed sheets will be bent in an awesome amount!

Density of Black Holes

Imagine the density of a black hole as follows: Imagine a mass of tens, hundreds, thousands, sometimes even millions, and billions of times larger than the Sun. Imagine that you've compressed all of this mass into a volume at a distance from one end of New York to the other.

You remember from your secondary or high school information: Density is obtained by the volume of the mass. Therefore, mass and density are directly proportional; volume and density are inversely proportional. Massive celestial bodies such as black holes are extremely large in mass and extremely small in volume. This means tremendous intensity.

The effect of such a dense mass on the space-time texture is an unbelievable deflection. This is called the gravitational well. This well deepens so fast that even the speed of light cannot overcome it. That is why the famous word emerges: Black holes have such a powerful gravitational force that even light cannot escape this gravitational force.

Here is the border around the black hole, where the light can not escape is called the event horizon. The event horizon is a term used to describe the most pronounced domain of influence rather than a black hole itself. The event horizon can be many times greater than the diameter of the black hole itself.