1 Black Hole is 10 Billion Times mass of Sun. Black Hole Explanation.


Sometimes physics seems to be strange than fiction. You may probably heard this lines if you are a follower of astrophysics. Then Do Black Hole really exists? Why this small medley is so important for physics? Why this black thing have billions of mass?

If these are your question then you are on right place. Hey Avidian, Let’s Start.


History of Black Hole

Black Hole history is so much complicated than any history of physics because it simple enough to just visualize and imagine Black hole but very difficult to place into in space. From Ismaël Bullialdus to Event Horizon Telescope, every work in this field can’t fully define what exactly Black Hole is.

An American Scientist John Wheeler emphasized that stars could eventually or at last collapse. Debate on this fact is very immense in physics, although very scientist believe in this fact.

The Idea of Space Time singularity was however coined by Physicist Stephen Hawkings. He then demonstrated “Black Hole” in his own way. In 1972 Stephen Hawking proved that the area of a classical black hole’s event horizon cannot decrease. In that same year James Bardeen, Brandon Carter, and Stephen Hawking propose four laws of black hole mechanics in analogy with the laws of thermodynamics and Jacob Bekenstein suggests that black holes have an entropy proportional to their surface area due to information loss effects.

In 2006 Event Horizon started collecting data and then in finally 2019 it gave us the very fist image of Black Hole on 10 April.

Black Hole image captured by Event Horizon
Image Credit NASA

What exactly Black Hole is and How it forms?

I will try to explain in it simple but very physical manner.

A star in it’s life oppose to it’s own gravity by thermal pressure. Thermal Pressure is a pressure that tries to expand the stars layer to outward.

Well you can see that gravity tries to contract but thermal pressure oppose. That’s exactly star work in his young life.
Image by NASA

But eventually star loses it’s energy, it loses it’s bank of thermal pressure. And then star began to contract. Then some of it contract to white dwarf, however Indian Physicist Chandrashekar showed that the maximum mass of white dwarf is 1.4 Times that of sun. This limit is known as Chandrashekar Limit.

But the question is what if the star breaks Chandrashekar Limit, that question was answered by Robert Oppenheimer in 1939. That he answered that such a star could not be supported by outward pressure and that if you take pressure out of the circulation then a uniform spherically systematic symmetric star would contract to a single point of infinite density. And that point is what we called Singularity, that was later examined by Stephen Hawkings.

If we conclude then , One Black Hole was initially a star that was collapsed by another star or by it’s own gravity and get fit into a space-time singularity where space and times comes to end. Black Hole is so dense that’s why gravitational energy that it have is so great that even a light that get inside that can’t exit from there.

Types of Black Hole

On the basis of mass and size black hole are of three types ;

  • The smallest ones are known as primordial black holes. These are smallest black holes and are small in size in compare to other.
  • Then medium ones are known as stellar black holes. The mass of a stellar black hole can be up to 20 times greater than the mass of the sun but it may be only about 10 kilometers across in size.
  • The massive ones are known as supermassive black hole. It is believed that every galaxy have a supermassive black hole in it’s center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has an estimated mass equal to about 4 million suns but its estimated size is about the size of our Sun only.

Image by Quora Writer

You may notice that black hole’s mass is so great but size is small when we compare with it’s mass.

The boundary of Black Hole is called Event Horizon from where gravity escapes.

Falling in black hole is just like falling in Niagara Falls, if you near the point from where water splash to downward then as fast as you can paddle fast from there the chances of survival are high.

Then why we can’t see black hole ?

Answer is Black Holes are not black they are just named like this, because of light get into black hole and that is other matter that it don’t reflect from there because of event horizon that’s why according to optics we can’t see black hole.

Why it does weighs so much

Because it gets denser and denser and contracted during it collapse mass gets bigger and bigger and bigger, and when size becomes small and density becomes immense, the mass scale goes up according to mechanics.


The pure answer of Black Hole is yet packed in that Black Hole, but for physics it is really important to draw those facts to understand universe.

First Maxwell Equation Integral Form aka Flux of Electric Field S01 B01

Fig 1.1 Image Credit physics.udel

Maxwell Law,

Probably you may heard of the precious set of equation in history of Physics, Maxwell’s Equation. In this series of blog I am going to explain as simply as I can and this is Blog 01, in which we are going to know the fascination of Physics.

Let’s come up to first equation which is often called Gauss Law for Electric Field. (Look in fig 1.1 for first equation). In which left side of equation is telling the flux over a closed surface of Electric field and right side represent the enclosed charge over permittivity of free space (e naught or epsilon naught). Wait but if you don’t have the idea of what is flux, surface integral, enclosed charge and permittivity of free spade, then don’t be worry here you will get all the need to understand this equation. But first let us grasp the idea of Gauss Law of Electric Field.

Electric Field produced by electric charge then flux of that field passing through any closed surface is directly proportional to the enclosed charge of the surface

Imagine there is imaginary surface on which charge is zero then electric flux must be zero.

Well if you are a beginner then you must have the problem with this equation, it is easy look up here, the first thing on the left side indicates the surface integrals and the E representing the magnitude of Electric Field which is vector and then is called dot product and then n is normal vector and da is increasing surface area in square meter. Then coming up to the right side we have q(enc) which is the enclosed charge and then ε0 which is permittivity of free space basically a constant.

Now I hope you have basic understanding about the different notation of equation.


The Electric Field

Electric Field

Fig 1.2 Image Credit physics.bu.edu

Electric Field is a real or imaginary field  and is a electrical force per unit charge exerted by the object

Well there is lot of debates on the definition of Electric Field but this one is so good. Well imagine a electrical object placed on a table and now see the outer field of object and now say it is electrical field. Well see imagination,

Imagining Electric Field, A is object and outside of that surface is Electrical Field.

Fig 1.3

Now let’s see the equation of Electrical Field –

E = F / q, where E is vector electric field, f is force and q is charge at that location. Then SI Unit of Electric Field is V/m and other unit as N/C.

  • Electrical Field is directly proportional to force.
  • SI unit of Electric Field is Volt per meter and other unit is Newton per coulomb.

Electric Field Lines

Electric Field Line can be visualize as the line travelling across the Electric Filed. It travels in the same direction of the field and is like a arrow like structure.It tells us about the strength of the field .

It is just like a demonstration of the strength of that particular field. The longer the lines and closer the field is stronger. Now go to fig 1.2 can you see the arrow like structure and that exactly the field lines are.

  • Electric Field line originate on positive charge and terminate on the negative charge (You can see in fig 1,2)
  • These Field lines never cross each other because that would reflect that field point toward two point which is impossible.
  • Electric Field lines are always perpendicular to the surface conductor in state of equilibrium.

Well there is a lot of electrical object and all of them have different equation so here is the list of few of them

  • Sphere which s conducting with charge = Q — E = 1/4piε0*Q/r*r unit ( r is distance from the center)
  • Point charge with charge q — E = 1/4piε0*q/r*r unit ( r is distance from the center)
  • Infinite line charge with linear density lambda — E = 1/2piε0*lambda/r*r unit

Well they are not difficult just some ugly but we will handle it out soon.

So E in the equation represent the total electric field at each point on surface.


For now it enough next time we will handle with dot product and n normal vector, to check schedule click on About Me.


Questions Section

  • Find the electric field on the center of a point charged meanwhile the point on which charge is present? (Note It is point charge). Answer in Comments.
Aayush Verma, Avidian Space

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