Basics of black holes

Previously, I have talked about white dwarfs and neutron stars. So in this post I will be talking about black holes.

So every star has some fuel inside its core. This fuel is basically hydrogen. This hydrogen gets converted into helium which releases a lot of energy. This works like a H-bomb. But anyways, this energy pushed the star outwards to prevent it from collapsing into its own gravity.

When a star, about 10 times the solar masses, loses all its fuel, the gravity of the stars compresses all the matter of the star inwards. So when it gets compressed, the density of the star increases. And at one point it collapses to a singularity, a region in space which has infinite density and no dimensions.

So if i had to express it mathematically, it would be something like this.

f(x)= 1/x, where x=0.

The answer is not defined. It does not make sense. Hence, laws of physics break at singularity. All the fundamental forces like magnetism, the weak and strong nuclear forces and gravity all become one.

At the singularity, time ends or stops. (I will be making a post on how this happens very soon.)

So the region around the the singularity is called a black hole and the boundary around the black hole is called the event horizon. The event horizon of the black hole is also called the point of no return as when you cross it, you do not return.

The gravity of a black hole is so much its escape velocity exceed the speed of light. So, nothing, not even light can escape the black hole.

Save the dying Aravalis

This post is different from my usual posts, as this wouldn't be about outer space. But rather about an issue on earth.

If you don't know, I am from India, specifically Rajasthan. And one of the largest mountain ranges in Rajasthan are the Aravallis, spreading from about 144000 to about 147000 sq. km.

They emerge from Delhi, pass through some parts of Haryana, Rajsthan (where most of it is located) and end in Gujarat. This mountain range is about 2-3 billion years old.

Recently, government gave a new 'definition' for the Aravalli Ranges according to which only the hills of Aravalli that are taller than 100 meters would be given protection. This means that the trees could be cut and the valleys could be mined.

And this is horrifying. Aravallis are not really tall. And a lot of the hills are not taller than 100 meters. And does a hill 99 meters tall does not fulfill its purpose? 

These ranges are what keep Rajasthan and a huge part of India alive. 

They stand between the Thar Desert and the rest of India, and prevent the sand and dust from coming into east India. This prevents the rest of the India from becoming a desert. They have many important rivers like Luni, and Chambal which are the main sources of water in many regions. 

The Aravallis which have held a great geographic and cultural significance will die due to the greed of the few in power. The Aravallis which have stood still all these years would fall onto its knees because someone wants to mine in those regions.

This is not development. This is an attack on the biodiversity of the country. This is the attack on all those people who drink the water from the rivers that Aravalli births. This is attack on the animals and the trees anf bushes of these ranges.

This is attack wrapped in the colorful packing of development.

I want all of you to raise your voice against this. If you cannot participate in the protests, then please post about it online so that more and more people realize the adversity of the situation.

gamma ray bursts

Gamma ray bursts are powerful explosions in space, which release gamma waves. 

But what are gamma waves? You see there are various frequencies and wavelengths of lights. Gamma waves have the highest frequency and lowest wavelengths. 

Gamma Ray Bursts (GRBs) are the second most powerful explosions in the universe, coming after, of course the big bang. 

They are mainly of two types.

Short GRB- These occur when objects like two neutron stars merge. They are shorter than two seconds.

Long GRB- they occur when a star collapses into a black hole.

The short shining, gamma waves are followed by the emitting of  longer glowing rays such as UV rays, microwave, infrared, X ray, etc. This glow could stay around for some days, weeks or even years if we are lucky.

Now, how do we detect these.

As you can see, they are very further to the range of the lights we can see. So one of the ways could be by detected by observing the afterglow of a GRB. But one of the interesting things is that the time we actually detect them, millions of years could have passed, because lights takes time to reach here.

But what if we not lucky enough every time and the afterglow does not last that long? What would we do in that scenario?

Well, if that is the case, then scientist use sophisticated instruments to detect them by their gravitational activies and the gravitational waves they create. If you wish to learn more about gravitational waves, then I also have post about them which you can find here.

brown dwarfs

Brown dwarf refers to a celestial body that is not big enough to be a star, and not small enough to be a gas giant planet. So about the size of 13 to 80 times that of Jupiter.

They are formed just as stars do, due to the gravitational collapse of dust and gas. However their cores are not hot enough at any point to sustain the nuclear fission of hydrogen. 

Nuclear fission basically means breaking down of a larger atom into smaller nuclei to release a lot of energy. However, they can fuse deuterium, which is an heavier isotope of hydrogen.

They don't radiate much glow and have lower temperatures compared to 'normal' stars.

The interesting thing is that they can also be orbited by planets. and besides they could also exist as binary systems.

If you want to know what binary systems are, I also have a post about them which you can find here. And more interestingly, they could even exist as binary systems with white dwarfs.

Brown dwarfs can also sustain life. but don't take this as good news as this is not sustainable because once the brown dwarfs start to cool down, that habitability would shrink.

And more importantly, they also have planet-like complex atmospheres.