Hello everyone! This is Ramesh here and today
we will know about one of the mysterious universe
object known as Black Hole.
A Black Hole is a region in space-time where
no matter or radiation can escape due to its
intense gravity. Even light can’t escape
from its gravity hence the name “BLACK”
hole.
Devouring nearby stars, radiations, emitting
strong gamma-ray bursts and X-ray radiation
in space are some of the common characteristics
of Black Hole.
We can make Earth black hole by crushing its
size to the size of a marble. Similarly, squeezing
sun to the diameter of 3 km will convert it
into a black hole. In the 18th century, John
Michell used the term “Dark Star” for
stars whose gravitational fields are too strong
for light to escape. In 1960 physicist Robert
Henry Dicke compared the phenomenon to the
Black Hole of Calcutta, a prison where people
entered but never left alive. The term "black
hole" was used first time in print by Life
and Science News magazines in 1963.
Stellar black hole form when a massive star
collapse at the end of their life cycle. Stars
having 3 or more solar mass can undergo extreme
gravitational collapse after consuming all
of its fuel. Gravitational collapse occurs
when an object's internal pressure is insufficient
to resist the object's own gravity. When the
Stellar black hole formed, it becomes more
massive by consuming space debris, nearby
stars, and even another black hole and eventually
become a Supermassive black hole having mass
ranges from millions to billions of times
than to our sun. They are located at the center
of each galaxy and our milky way is no exception.
The supermassive black hole at the center
of our milky way galaxy is named Sagittarius
A*. It is around 26,000 light-years away from
the Earth and 4.3 million times more massive
than the Sun.
When radiations, gas, dust and other space
debris got attracted by the black hole they
start spinning and form a horizontal thin
strip of spinning matter around the event
horizon which is known as “Accretion disc”.
The event horizon is the boundary through
which matter and light can only pass inward
towards the mass of the black hole. Nothing,
not even light, can escape when it crosses
the event horizon because the escape velocity
needed exceeds the speed of light. At the
event horizon of a black hole, the space-time
deformation becomes so strong that instead
of bending, light falls into it as there is
no way out.
The Schwarzschild radius was named after the
German astronomer Karl Schwarzschild who provided
the first exact solution to the Einstein field
equations of general relativity.
The formula of the Schwarzschild radius is
rs = 2GM/c2 where G is the gravitational constant,
M is the object mass, and c is the speed of
light.
According to general relativity, the gravitational
singularity may lie at the center of the black
hole. Gravitational singularity is a region
where space-time curvature becomes infinite.
This singular point may have infinite density
and contains all the mass of the black hole.
Anything that crosses the event horizon will
be carried into the singularity. In this journey,
it will be torn apart as spaghettification
occurred by the growing tidal forces. After
that, it will be crushed to infinite density
and their mass is added to the total of the
black hole.
The following set of animated movies visualizes
the size of stellar and supermassive black
holes in the Universe. Let’s watch...
