June 21, 2020
We live in a universe that is boundless and is impossible for us to wholly understand or
completely see. This is not only because it is so large but, also because it is
expanding at ever-increasing rates. Therefore, we are only limited to see the
part of the universe which we call the observable universe. According to
current estimates, the observable universe is about 93 billion light-years
across.
The universe
is home to countless types of celestial bodies among which, some are just too
complex for our tiny brains to understand. The common celestial bodies that
exist are planets, stars, galaxies, nebulae, etc. However, that is not it.
Among the universe, exists a monstrous celestial body of whom, the gravitational field is so strong that nothing, not even light (the fastest
traveling entity) can escape the grasp of these monsters.
Many of you
may have prior knowledge about black holes because they are all over the
internet. You will find thousands of videos on what black holes are, how do
they form, where do they form. Therefore, in this blog, I will briefly explain
what these monsters are.
I will come
to the explanation of my title later on but for now, let's start with what
these are and how do they form. Black holes are regions in space where gravity
is so strong that nothing, not even light can escape its grasp.
These monsters
are all over the universe. In fact, We have one humongous black hole at the
center of our galaxy too. Besides, there are millions of smaller black holes wandering about in our galaxy.
The idea of
black holes were first proposed by a geologist named John Mitchell in 1783.
These objects were referred to as dark stars that were so compressed and dense
that the escape velocity from these objects was faster than light. He also gave
evidence of how these objects could be found in space. He explained that if you
were to find a star system with two stars in which the only one was visible, the
second object with the star surely is a black hole. However, this idea was
rejected and forgotten for two centuries since it seemed so illogical and
impossible back then.
Moreover,
let's explain how black holes are born. Before this, however, we need to know
that there are three types of black holes, primordial, stellar and
supermassive, and each of these forms in their own ways. The first and smallest
type is primordial black holes. These can be as small as a mountain but can
still possess the mass of a mountain. These were formed soon after the big bang
when radiation dominated the universe.
Furthermore,
the next type of black holes which are larger than primordial ones is stellar
black holes.
A 10-mile stellar black hole can possess a mass almost 20 times
larger than our Sun. These black holes are formed when a massive star collapses
onto itself after it runs out of fuel at the end of its life in a supernova
explosion. This explosion can either give birth to either a white dwarf,
neutron star, quark star depending on its mass. However, if the mass surpasses
a limit called the Tolman-Oppenheimer-Volkoff. It will collapse until a stellar
black hole is formed.
Lastly,
there exist supermassive black holes that can possess the mass of millions or
even billions of Suns.
These types of black holes can be found at the center of
galaxies. In fact, a supermassive black hole known as Sagittarius A* is located
at the center of our Milky Way galaxy. It is commonly known that these types of
black holes start small but end up becoming humongous monsters. However, it
isn’t really clear how these black holes came into being in the first place.
One theory suggests that they either formed due to the merging of many clusters
of black holes that collided together and another one suggests that they formed
in the early universe when large clouds of gasses collided together.
This was the
end of the first blog of this series. I will explain more about black holes in
my next blog of the series.
