Do you remember the last time you looked up at the sky? When was the last time you looked up at the sky for no other reason than to see the stars?
That shining, shimmering sea of tiny little dots glowing ever so wonderfully. Now, don’t get me wrong, I know pollution is a thing, and all the visible light from cities makes it increasingly difficult for most of us to see the true night sky.
But, oh, is it not magical? It is incredible to think of those massive stars, and it always ignites a sense of wonder in me. There are like a blanket over our heads, a blanket of bright burning balls of fire, so ferocious and so very far, they merely look like stardust.
I remember being a small kid and looking up, thinking of the most magical and absurd stories involving stars. The curiosity bubbled over, and I thought, what are stars made of?
I must admit that the explanation he gave was not to my liking back then – I was expecting something more mystical. I would have preferred if he had said that some magical being had sprinkled fairy dust all over the universe.
But now that I am older, this explanation seems all the more unbelievable to me. So, what are stars made of? Where do new stars come from? Let us find out how stars form.
Star Formation: What Are Stars Made of?
Let’s answer the ever exploding questions, what are stars made of.
In the most basic sense, stars are quite literally exploding, burning balls of gases, mainly hydrogen and helium. Instead of being made up of solid materials, like our own Earth and other planets, stars consist of gases.
They are also found to contain trace amounts of heavier elements such as oxygen, carbon, nitrogen, and iron. This property is similar to how the Earth’s atmosphere is made of different gases.
Have you ever heard of a hydrogen bomb? They are incredibly powerful bombs that operate on the rapid release of energy that occurs during the nuclear fission of deuterium and tritium, which are hydrogen isotopes.
Well, what happens within a star is not all that dissimilar to the process of a hydrogen bomb – it just happens on a far larger scale. The so-called cradle of all the stars that we see is within galaxies. Here is where nebulae occur.
Nebulae are massive clouds of gas and dust, also called molecular clouds. Inside these, gravity tends to make tightly compacted clumps or incredibly dense pockets. That is where the magic of forming a star begins.
The temperature begins to rise higher and higher until it reaches millions of degrees. The hydrogen atoms present in the nebulae amalgamate to form atoms of helium, its neighboring element. This is a nuclear reaction called nuclear fusion, and it is the secret behind how new stars starts its life.
Stages Of A Star
So far, it sounds simple. Well, this is the least technical way to explain it. There is a whole lot more that goes on behind star formation, so let’s dig a little deeper, shall we?
Remember those dense pockets in the nebulae, the molecular clouds? Due to the ever-present phenomenon of gravity, the cloud collapses under its weight.
This leads to the developing stage of the star, during which it is known as a protostar. These protostars are hidden behind clouds of dust present in the nebulae in a celestial game of hide-and-seek.
You would think that like humans get taller and larger as we grow, so would stars, right? That is not the case! Protostars decrease in size and get smaller as their life cycle goes on. There is a reason behind this – it allows the star to spin faster and faster, its acceleration increasing.
This occurs due to a little something called conservation of angular momentum, a physical property of a rotating or spinning object. It states that when no external torque acts on an object, no angular momentum change will occur.
To make sense of this, let us take the example of a spinning ice skater. We all must have seen that when they begin their great spins, they tuck in their arms during the performance of an ice skater.
There is a scientific explanation for this! An ice skater spins with higher speed when their arms are tucked in. This action reduces their moment of inertia (the property of an object to remain at rest or in motion) even while their angular momentum remains constant.
This creates a rise in pressure, which leads to a rise in temperatures. Before we know it, the star has moved onto the next evolutionary stage – a brief phase known as the T Tauri phase. Well, if you can call a phase that lasts a hundred million years brief.
Now, the temperature at the core of this incredibly dense region has to rise to around 15 million degrees celsius before nuclear fusion can take place and hydrogen atoms join to form helium. Now comes the longest stage of a star’s life, known simply as the main sequence.
Such stars in the main sequence phase are known as main-sequence stars. Most of the luminous stars in the Milky Way, our galaxy, fall under this category. This includes our very own Sun.
Now, you might be wondering, “If the stars are in a constant state of nuclear fusion, does that not mean they are in a constant state of a nuclear explosion?” Surprisingly, and terrifyingly, you are right.
Stars in the main sequence, including our sun, are in a stable sequence of nuclear fusion. They convert hydrogen to helium and emit a massive amount of energy, which maintains the brightness and heat of the stars.
But fear not! The Sun and other stars also have huge amounts of hydrogen within them, which act as fuel for nuclear fusion reactions. They have such large hydrogen reserves that they can sustain them for billions of years.
The nuclear fusion reactions produce so much energy that the Sun is just a big shining ball of plasma. Plasma refers to the ionized gas that includes positive ions, free electrons, and protons that have been stripped away from hydrogen atoms.
This plasma is responsible for about 90% of the Sun. Every second, there are thousands of protons colliding with one another in the core of the Sun to create helium nuclei.
The energy released by the luminous stars that we experience in the form of the heat we feel and the light we see is known as electromagnetic radiation.
At the same time as the radiation is being given out, there is also convection near the Sun’s surface, during which the heated gases rise, cool down, and sink back to the surface. These electromagnetic radiations are why we can see stars in the night sky and find them on radio telescopes.
Types Of Stars
There are many different types of massive stars in the Milky Way and beyond, all in different evolutionary stages. The nearest star to us, the Sun, is a dwarf star in its prime of life, as aforementioned. There are also white dwarf stars, red dwarfs, red giant stars, and neutron stars, among others.
White dwarf stars are formed when a star about our Sun’s size has used up all the fuel it can, and it collapses under its gravity.
The resulting white dwarf star is tiny compared to other stars, emitting much heat but not much light. A white dwarf is made even harder to spot because most of the energy it emits is in the ultraviolet spectrum and invisible to our eyes.
Red dwarfs are the most common stars in our universe – they are main-sequence stars but have very low mass. These stars burn slower, will live longer, and are cooler stars than our Sun. They have a dim red glow and are not easy to spot with the naked eye.
Red giant stars are aging stars that are formed when the hydrogen in their core runs out. To maintain survival, they begin utilizing the hydrogen present outside the core. Nuclear reaction continues in a shell surrounding the star.
However, this leads to red giant stars dramatically increasing in size. In their last desperate attempts, they even burn up the helium and heavier chemical elements in their core, leading to large stars called yellow supergiants.
Neutron stars are the result of a star that is sufficiently massive. About five times the mass of the Sun collapses.
This causes an exhale of powerful enough energy to force electrons and neutrons to merge and create a neutron star. A neutron star is made out of neutronium and composed entirely out of – you probably guessed it – neutrons. They are dark, small stars.
Solar-type stars (sun-like stars), blue stars, orange dwarfs, supergiants, all present within, if not our galaxy, then our universe. Out of all of these, there is one star in our solar system – Sol, the Sun.
We sometimes take the presence of the Sun for granted. It is amusing how many people cry out “Proxima Centauri!” and pat themselves on their back when asked about which star is nearest to us.
However, the Sun is present in our very own solar system that is closest to us and of the utmost importance to all the planets.
The Sun sustains us, but did you know that all the planets in our solar system are an aftereffect of the Sun’s birth? The leftover material from the star formation created new planets.
The Sun is approximately 4.6 billion years old, which puts it in an average-sized yellow dwarf star alongside multiple stars. Experts predict that the Sun will remain in the main sequence for several billion more years.
While our Sun seems to be unbelievably hot – so much so that we have not dared to go on an expedition anywhere near it, even with the high-tech equipment we have at our disposal – it is astonishingly one of the cooler stars. The surface temperatures of the Sun are about 5778 K.
It has been discovered that the color of a star corresponds to its temperature. Blue or white stars are the hottest, while warmer colored stars like red, orange, and yellow are comparatively cooler.
But remember, for next time you are near a fire – the white and blue part of the fire, nearest to the center, is far hotter than the yellow parts. It is quite mind-boggling.
Some stars might shine brighter than others, which is a factor in how much energy they release, known as the star’s luminosity.
The distance from Earth affects the star’s luminosity- naturally, stars that are farther away seem dimmer than stars in a closer solar system.
The Death Of A Star
There is life, death, and a star is no exception to this universal truth. The stars’ evolutionary stages take place over billions of years, but eventually, they come to an end.
Curiously enough, the length of a star’s life is inversely proportional to its birth weight. This means that a yellow star with a low mass will live for a very long period and comparatively more than stars with a higher mass.
Large stars with mass many times greater than our Sun will only live for about a few million years. This may seem like a lot, but other smaller stars, like red dwarf stars, can have a life span of ten trillion years – or more!
The Sun is presently at the prime time of its life. It will continue to remain in a stable state for another five billion years or so, after which it will increase size. This increase in size is caused by the fact that most of the hydrogen atoms joined to form helium at this point.
The helium sinks to the star’s core, and consequently, there is a temperature rise. This led to the star’s outer layers of hot gases expanding. At this point, it is known as a red giant.
The process of nuclear fusion will come to a complete halt, and it will simply stay in our solar system and cool. This will be followed by a stage of fading, in which the star’s outer layers are let go. At this point, it is known as a white dwarf.
Soon, even the white dwarfs will cease energy production and go dark. This stage – where the star is a black dwarf – takes such an immense amount of time to reach that scientists have never observed it, and it remains purely theoretical.
There are no known stars that have become black dwarfs. Since the early universe, any white dwarf that has been formed has been thought to have lost only 0.2% of its total heat.
This is one path, usually taken by stars of a similar or same size as the Sun’s. However, the most massive stars tend to go down a different road.
The stars may seem to be red giants on the outside, but their core contracts become so incredibly dense that it collapses and explodes. This phenomenon is known as a supernova explosion.
Maybe the most massive stars take this path as a way to make up for their short life spans – a spectacular death to make up for a million years they spent alive and sparkling. Their deaths are far more magnificent than the quiet fading of other stars.
After the supernova explosion occurs, a compact core of the remaining material is left behind that becomes a neutron star.
If, however, the core is big enough, it can lead to the formation of a black hole instead. A black hole refers to space where the gravity is pulled so tight that not even light can escape.
Nuclear reactions in the massive stars lead to the production of iron in the core. The star has no way of supporting its mass, and the iron core collapses. Once it has achieved iron, all the energy taken from nuclear reactions is fulfilled – production of more heavy elements uses rather than producing it.
As a supernova’s path of destruction and luminosity as predictable for astronomers, it is often used as a marker in the vast distances of the galaxy.
They are astronomical marking tools, or so-called ‘standard candles’ and are a great help in measuring the universe’s expansion. Think of them as celestial distance stones.
That raises the question – what is in between stars? Well, the space between stars is known as the interstellar medium.
The interstellar medium contains a whole lot of gas and dust. These regions also contain molecular clouds, or nebulae, consisting of a large variety of molecules, including hydrogen. These molecular clouds are where new stars form.
Everything Comes From Stars
Remember the process of nuclear fusion, where hydrogen combines to form helium? These helium atoms later act as the building blocks to form the trace amounts of heavier elements in the core, like carbon.
Now, do you know that carbon goes on to become the building blocks for life? For us? It’s true! Carbon is at the heart of all the chemicals that we are composed of.
It is something to think about the next time you are looking up at the stars – we are, all of us, quite literally made out of stardust.
Over billions and billions of years, we have evolved to the point that we can look up and consciously think about where we were – carbon in the heart of a star – to where we are – stargazing at objects that are seemingly so close but impossibly far.
We exist because stars exist. There is more that we do not know about stars than we do. For starters, we are clueless about the actual number of stars out there. Sure, we have an estimated 200 billion trillion stars in the universe, but that is only in the observable universe. We do not even know if the universe is infinite – which is a very real possibility.
So, there you have it. Stars are some of the most incredible things to think, research, and talk about. I genuinely believe we do not think about them enough, and these wonderful, incredible, astonishing objects are beyond our wildest dreams.
While I have covered some basic information about stars, it is probably not enough to diminish your curiosity. You are probably now more curious than ever before, with questions popping up out of every answer you receive.
What happens inside black holes? What will happen to stars at the end of the universe? What is the end of the universe? How did the first stars come into existence? This curiosity will keep the endless search for knowledge alive.
But at least, now you know what are stars made of and how they were made.
I hope you have enjoyed this article. If you liked this, be sure to check out Gravitational Waves-The Past, Present, and Future!