We all see the sun and stars shining in the sky every day and every night. These all are the most important part of our life and the universe. But the question is how much you know about the stars. The basic thing that everybody knows is that the star is something that shines and is very very hot. Some science people also know that there is a constant nuclear reaction going on in the star. But fewer people know about how the stars form, from where they have come, and how they are going to die. And many more things we don’t know about the stars. So in this article, we are going to Discuss the star. And we are going to provide every essential knowledge about the stars. So let’s start the wonderful journey of stars.
A star is a naturally occurring physical entity in space. They are spherical and very huge. They are the self-luminous celestial bodies in space. In most of the star’s active life, there is a nuclear fusion of hydrogen into helium. This fusion occurs in the star’s core. The energy emitted in this nuclear fusion is the main reason behind the shining of the star. The universe contains billions and trillions of stars. But very few are visible to us with naked eyes.
The formation period of the stars is very large. The formation of stars takes place in the vast clouds. In these vast clouds, thousands of stars are born at a time. These vast clouds are cold, dense, and they are mostly made up of hydrogen gas. At an early period of the birth of a star, they are huge spinning globes of hot and glowing gas. These gases are hydrogen (mainly), helium, and a small part is of other gases. Most of the material is tightly packed in the star’s core. It is the star’s core where nuclear reactions take place, which releases energy in the form of heat and light. Now let’s discuss the formation process in detail.
The process of the formation of new stars
The clouds in which stars are formed are usually stable. But due to some disturbance, the cloud becomes unstable and breaks into small pieces and fragments. Then comes the role of gravity which puts all these fragments into a tighter clump. As the clump gets tighter or shrinks it starts forming into a spherical shape. And after that, the core starts getting denser and hotter. By the time the temperature and pressure got so high that it initiated the nuclear reaction. And due to this nuclear reaction in the core, the star starts to shine.
Stages of formation
To make it easier to understand, let’s discuss its stages of formation. So there are six stages of star formation, and they are as follows.
- Interstellar cloud: As we already discussed, the stars form huge, cold, dense clouds of gas and dust. And this process of formation of stars starts in those clouds only if something disturbs the cloud. Mostly this disturbance occurs when this cloud collides with the other cloud or due to the shockwaves which come from supernova explosions.
- Fragment formation: Now, due to the disturbance, the cloud breaks into fragments of different sizes and masses. Here comes the role of gravity, which pulls the most massive and denser fragments into tighter clumps. By the time these fragments start shrinking, and eventually they clump turn into protostars.
- Protostar: After the formation of protostar, there is enough gravity developed. And this gravity pulls the material into the core of the protostar. And due to the accumulation of material into the core, the density, pressure, and temperature are gradually increased. The more the accumulation of matter at the core, the more the rise in temperature and pressure.
- Spinning disc: The increase in the mass at the core creates a gravitational pull. This gravitational pull attracts more gas and dust towards the core. Due to this event, powerful winds developed near the core. And blowing jets of gas coming out from the center also developed.
- A star is born: Due to all these events of accumulation of material, and gravitational pull that attracts the gas and dust, the temperature and pressure increase a lot. And the core of the protostar becomes so hot and dense that it initiates the nuclear reaction and the star starts shining. The glowing core then produced a pressure directing outward. And this outward pressure balances the inward gravitational pull and the star becomes stable. It is now known as a ‘main sequence star’.
- Planet formation: Some material remains after the formation of stars. This remaining matter starts revolving around the star in the form of a spinning disk of dust and gas. Now, there are two possibilities: one is that this debris may be lost in space. While second is that it may clump together and form planets, moons, comets, and asteroids.
So we discussed how stars form or take birth. But after that, how they live and what about their end. All these questions are answered in this section of the article. If we talk about the death of the stars, every star dies when it runs out of fuel. The different stars die in different ways depending on their properties, like how much mass they contain and how powerfully their core is squeezed by gravity.
Like earth, it is the force of gravity that squeezes the hot core of the star. And this force of gravity is generated by the star itself. And it depends upon how much matter the star has. If a star has more matter it means more will be the force of gravity and more gravitational force more will be the compactness of the core hotter and denser core. As we already discussed, stars generate heat and light through the process of nuclear fusion. That nuclear fusion occurs in the core where hydrogen atoms turn into helium, and this reaction releases energy.
When small stars run out of fuel, their light fades away slowly. But when massive stars run out of fuel they turn into supergiants and then supernovae occur which either convert them into a neutron star or a black hole. When a larger star dies, it turns its hydrogen into heavier chemical elements such as carbon and oxygen. These elements are then recycled to form new stars or planets. There are four ways in which a star can die.
Every star goes through a phase when it is young and stable. In that state, it shines constantly. Let’s discussed the different ways in which a star can die one by one:
Stars, which have less mass than half of the mass of our sun, come under this category. When all hydrogen of the core of these types of stars is used, they start feeding off the hydrogen in its atmosphere. But it doesn’t generate enough gravity to use other elements as fuel, so it slowly shrinks to become a black dwarf. The black dwarf looks like an earth-sized cinder, which means an earth-sized star without any flame or shine. You will be amazed that this process is so slow that it takes far longer than the age of the universe. This process approximately takes up to a trillion years.
All-Star like our sun comes under this category, which means all Star having the mass equivalent to our sun’s mass. When these types of stars run out of fuel in their core, nuclear fusion spreads outside the core. Due to this, the star expands into a red giant. The core collapses until it is hot and dense enough to fuse helium. But by the time it ran out of helium too. And finally, it becomes a white dwarf and its outer layers spread into space as the cloud of debris.
Since nuclear fusion spreads to the layer of the star, which heats the layers of the sun and makes it expand. And when a star starts expanding, eventually it becomes a red giant. Interestingly, nearby planets to the star may be swallowed by that growing star giant. The outer layers of the star dispersed into space and became a cloud called a planetary nebula. The material of this cloud is recycled to form a new star. And the core of the star becomes an earth-sized white dwarf. That white dwarf slowly fades and becomes a cold, dead black dwarf.
The stars which are approximately eight times more massive than our sun come under this category. They end in very strange and violent ways. In these types of stars, the heat and pressure in the core become very high. These conditions help make hydrogen atom fusion into helium feasible. And also make helium and larger atoms fusion possible to create elements like carbon and oxygen. And due to all this, the star turns into the largest star of all, known as a supergiant. Supergiant can grow up to 1 billion times the volume of the sun.
Now the star has become a supergiant. The nuclear fusion inside the core forces atoms to heavier and heavier elements. This process continues until the star’s core turns into iron. And after that, the star’s core is no longer able to generate enough outward pressure to resist the crushing force of gravity. Now, this star suddenly collapses and causes the deadliest explosion called a supernova. The supernova explosion is a billion times brighter than the sun. The outer layer of the star is blasted in space but the core continues to collapse by itself.
Two possibilities of massive star to become
The next step of the process depends on the size of the core. If the size of the core is smaller it becomes a neutron star. But if the core is massive then it never stops collapsing and it shrinks until it becomes a billion times smaller than an atom and finally it becomes a black hole.
The neutron star is just a few kilometers wide in size. But it’s three times heavier than the sun. Neutron stars are very dense and fast-spinning stars. And if we talk about the black hole the force of gravity near them is so high that even an object traveling at the speed of light cannot escape from it. Anything which falls and inside the black hole is torn apart by gravity and then crushed into a point of infinite density.
Types of stars
As we already discussed, the reason behind the shining of a star is energy. And this energy is released from the nuclear fusion of hydrogen into helium into the star’s core. At this stage, the star is known as the ‘main sequence star’. And the main sequence stars are different in color, size, temperature, brightness, and the amount of matter they contain. These factors help us in differentiating the stars. As we already discussed, these factors are also important in determining when the star ran out of fuel and how it is going to die. Either it is going to convert into a red giant or it is going to shrink to become white dwarfs.
Astronomers used the Hertzsprung-Russell diagram’s famous graph to classify the stars. This graph is plotted between the temperature and the luminosity. It mainly indicates that there are types of stars such as the main sequence star ( ordinary one) and red giants ( stars that are dying). Astronomers also divide the star based on their color such as the hottest are blue and the cooler ones are orange and red.
Interesting terms to know
Now let’s take an overview of the most essential component of star formation- clouds. In space, the clouds of gas and dust are known as Nebulas. Much of the gas and dust in the nebula are the remains of the old stars that exploded when they ran out of fuel. So this means after the death star leaves the material which was used in the formation of a new star. And interestingly over millions of years, this material is recycled to make new stars. It’s amazing to know that the star birth Nebulas are among the most beautiful objects in space. The blue light emitted by the newborn stars illuminates the colorful clouds of the nebula. Which makes the view more beautiful.
Orion Nebula is the closest nebula to our Earth. In the night it seems like a fuzzy star in the sword of Orion. But in reality, it’s a vast cloud of gas and dust. And also Orion Nebula is thousands of times bigger than our solar system. So you can imagine how big the Orion nebula is.
We already discussed that there is the formation of many stars at a time in the interstellar cloud. This means stars are not formed singly. They form in the group (clusters) from the same cloud and almost at the same time. And eventually, they all move away from each other. And exist alone in a space or with a close companion. Nearly half of the stars near to us in space exist alone, like our sun. About a third of the stars in space exist in a pair that is bounded by gravitational force.
The Pleiades cluster is a cluster that is made up of nearly 5,000 stars. And it can be seen with naked eyes. There is a prediction that says that in nearly about 250 million years after there will be no cluster of stars as all-stars will have dispersed.
I think now you have sufficient knowledge about the stars. So now you know the definitions, how stars come into existence, and how they die. We already discussed that stars shine due to the energy emitted in the nuclear reaction in the core of the sun. Stars take birth from a cloud of dust and gas. During birth, stars go through various stages. Many stars take birth at the same time from the same cloud. And Eventually, these stars get away from each other. They live their life up to trillions of years and they die. How a star is going to die depends upon its mass. Some die silently and some die violently by supernovas. But at the last level of their death, they form the elements which are recycled to form new stars.
we also come across How the classification of stars is done by astronomers. The classification is done based on their luminosity and temperature. We also came across some interesting terms like star birth Nebula and star clusters. Stars are the most important part of space and we can’t imagine our life without stars (sun). So knowing about them is essential for us. Hope you enjoyed the article.