Everything you Need to Know about Black Holes

We have a very powerful force residing in every galaxy in our universe, and they are called black holes. They are products of how the universe evolved, just like galaxies, stars and planets.

What Are Black Holes?

Black holes are some of the strangest and most fascinating objects found in the universe, but don’t let the name fool you. A black hole is anything but an empty space. Black holes are remnants of old or former stars that are so dense that no physical matter or even light can escape its powerful gravitational pull. Think of a star that is 10 times more massive than the Sun and then squeezed into a sphere approximately the diameter of New York City.

While most stars end up as white dwarfs or neutron stars, black holes are the last evolutionary stage in the lifetimes of enormous stars that had been at least 10 to 15 times more massive than the sun in the solar system.

In the theory of general relativity, it was predicted that a sufficiently compact mass can deform spacetime and form a black hole. The boundary of the region from which escape is not possible is called the event horizon.

Although the term or name “black hole” was not used until 1967 by Physicist John Wheeler, the idea of an object in outer space so big or massive and very dense that light could not escape has been around for many decades. Albert Einstein first predicted black holes in 1916 with his general theory of relativity and then John Wheeler first used the term and the first black hole was discovered in 1971.

One good visual representation of a black hole called “Gargantua” is in the science fiction movie “Interstellar”. It was co-produced by Caltech theoretical physicist Kip Thorne, whose work inspired the film and acted as a scientific consultant.


How Are Black Holes Born?

Whenever a giant star reaches their final stages of their cosmic life, they often explode known as supernovae. These kinds of massive explosions scatter most of a star into the void of space, but it leaves behind a cold remnant on which fusion is no longer present.

Younger stars have fusion that creates energy and constant outward pressure that exists in balance with the inward pull of gravity that is caused by the star’s own mass. In dead remnants of a massive supernova, no force is opposing the great pull of gravity, thus the star remnant begins to collapse on itself. And with no force to counterbalance gravity, a black hole shrinks to zero volume at which point that it is infinitely dense. The dead star’s own light is trapped in orbit and the dark star becomes a black hole.

The Three Types and Classification Of Black Holes

Black holes are classified by their mass, magnetic field and spin. On the basis of mass, there are three types:

  1. Miniature Black Holes. This type of black hole is believed to have formed during the Big bang and there is no evidence to debunk its possible existence during the evolution of the universe. The mass of this type would be considerably smaller than that of the Sun and it only formed because of the extreme external pressure during the Big Bang that compresses the mass to create a singularity.
  2. Stellar Black Holes. When a larger star collapses and continues to fall in on itself, stellar black holes are born. These types are small but incredibly dense and packs three times or more the mass of the sun. According to some physicists, the Milky Way contains a few hundred million stellar black holes.
  3. Supermassive Black Holes. These are the biggest black holes discovered. Many scientists believe that these black holes occupies the centre of the galaxy and increase in size as they pull in the more material from the dense core of the galaxy. And unlike the outer parts of the galaxies, the inner region is crowded with millions of stars and it creates favourable conditions for supermassive black holes to grow. The size of these black holes can be hundred thousand solar masses.


Classification of Black Holes

Black holes are also classified according to their spin and the magnetic field. The classification is based on Albert Einstein’s General Theory of Relativity.

  1. Schwarzschild Black Hole. It’s the simplest among the three classes and has only a theoretical existence. It has neither spin nor field. This class was proposed by Karl Schwarzschild and is characterised by a point of singularity and the event horizon.
  2. Kerr Black Hole. This class has both spin and magnetic field and is the most common black hole. It has a characteristic rotation on a central axis. It’s named after Roy Kerr, who proposed its existence. The Kerr black hole features a ring singularity, two event horizons, an ergosphere and a static limit. The Ergo Sphere is an ellipsoidal region outside the outer horizon where the space-time continuum rotates with the rotation of the black hole.
  3. The Reissner-Nordstrom Black Hole. This class is characterised by singularity and two event horizons, and show no rotation. It also has only a theoretical basis since it has no rotation.

What’s Inside A Black Hole?

As no one or nothing has ever gone inside and observed it, humans will never know for sure, but many physicists theorise and believe that as anyone or anything approaches the event horizon, none or nothing escapes. The speed of the event horizon exceeds the speed of light.

Inside the event horizon, calculations suggest that what the fabric of space-time will depend on the specific black hole’s history. It can be turbulent, twisted or any other things. Some say a person will surely die or it can lead to another dimension or galaxy. According to theory, within a black hole is a singularity where all matter in a black hole gets crushed.

What Happens If You Fall In A Black Hole?

Assuming that you start outside of the event horizon of the black hole. As you look towards the black hole, you will see a circle that is perfectly dark. Around the black hole, you will see the stars of the night sky. The star patterns will be distorted because the light from the distant stars will be bent by the black hole’s gravity.

As you fall into the black hole, you will move faster due to acceleration by its gravity. Your feet will feel a stronger gravitational pull as compared to your head because your feet are closer to the black hole. Your body will be stretched apart and for smaller black holes, the pull will be so strong that the body will be torn apart before reaching the event horizon.

If let’s say, you fall towards a massive black hole, the body will remain intact even if you cross the event horizon. But once you reach the central singularity, you will be squashed into a single point of infinite density. You will become one with the black hole.


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