Types of Black Holes

As observed by scientists and astronomers, all black holes are not exactly the same. Black holes are completely classified by only three conditions: mass, rotation, and charge.

Classification black holes according to rotation and charge :

1. Schwarzschild Black Holes
   
   

Non-rotating black holes are called Schwarzschild black holes. These black holes don't have rotating cores and have two main properties: a singularity and an event horizon. These holes don't have any electrical charge. It is characterized solely by its mass.

2. Kerr's Black Holes:

Rotating black holes are termed "Kerr black holes. These black holes rotate because the object that collided into the black hole was originally rotating. 

They have four main properties: 

• A Singularity 
• An Event horizon
• The Ergosphere
• The Static limit. 

There is no presence of electrical charge in these holes.

3. Black Holes with Charges:

There are two types: A charged and non-rotating black hole is called a Reissner-Nordstrom Black Hole.

When a charged, rotating black hole is known as a Kerr-Newman Black Hole.

• According to the classification by mass, there are 3 types:

1. Stellar mass black holes.
2. Intermediate Mass Black Holes
3. Supermassive Black Holes.

Stellar Black holes - small but strong

   These types of black holes are comparatively smaller in size than the other two. Their sizes range from a few 5-6 solar masses to a few hundred times the solar mass. So, when a star with a core twice to three times the size of our sun burns completely to iron, its energy production ceases and it collapses into a stellar black hole. These black holes are also called Kerr black holes as the rotation of the original massive star is conserved during the time of collapse and it contains very little electric charge. These black holes are mostly uncharged and rotate along their own central axis.

Finding a black hole is very hard since the radiation emitted cannot escape the gravitational pull of it. But the way in which the scientists found them is through an X-ray binary system. When the gases from the star nearby to it or acting as a companion to it are sucked into it, x rays are produced by these gases, which heat up to millions of degrees. So far, nearly 20 x-ray binary systems with a stellar black hole have been discovered so far.The nearest stellar black hole is V616 Monocerotis, which is nearly 3000 light-years away from us and nearly 10–14 times as massive as our sun.

Intermediate black holes - stuck in the middle

    The size of these black holes varies from 100 solar masses to nearly a hundred thousand times the mass of the sun. These black holes are certainly larger than stellar black holes, but not as large as supermassive black holes.

The true surety of finding these black holes is still a mystery, but many intermediate-mass black holes are found in our galaxy and nearby due to the accretion disc and gas cloud spectral. The strongest result which shows that these black holes exist is the low luminous active galactic nuclei that are the centre of the galaxy and have a comparatively higher luminosity, which is certainly not exhibited by a star. The origin of these types of black holes is determined by these three ways.

They were formed at the time of the Big Bang, so they are primordial black holes. Secondly, by the merging of stellar black holes and other smaller objects together. The third way is through the collision of massive stars in a dense stellar cluster.

 

Supermassive black holes - Giant-Sized 

     These are the largest types of black holes, being the size of a few thousand to millions of times the size of our sun. These black holes are very large compared to the other two types of black holes. Because of being so large, the density of these black holes is less than the stellar and intermediate-mass types of black holes. As we know, the Schwarzschild’s radius is proportional to mass, so for spherical objects, the density of objects is inversely proportional to the square of mass. So, the larger the black hole, the lower the average density. The pull of the supermassive black hole is also weaker than the other two black holes inside the event horizon.

     The origin of these types of black holes is still an open mystery, but still, as long as there is a black hole at the centre of every galaxy, it continuously grows by feeding the matter around it or by merging with other black holes. The active galactic centre of galaxies is where most of the supermassive black holes exist that continuously engulf the matter and are the source of the extreme luminosity at the center.

The supermassive black hole at the centre of our Milky Way galaxy is Sagittarius A*. Its diameter is said to be 44 million km and it is about 25,640 light-years from Earth.

Still, there are many more things to know about black holes, which we will discover slowly one by one.