Formation of The First Stars and Galaxies
Have you ever wondered how the formation of the first stars and galaxies was made possible? Well before deep diving into the topic, we must try and understand what are they a part of. Stars and Galaxies are all subsets of the Universe.
Consider the Universe as a set containing all the elements like stars and Galaxies and meteors and comets and various other entities which are strangers concepts to humans. Before learning about the formation of the first stars and galaxies we must learn about the universe that contains them.
1. Early Universe
Before the very formation of the first stars and galaxies, many other events unfolded that led us to the present. The universe is a very sophisticated entity, It could be in a nutshell defined as an Entity that consists of Space, matter, and time. To know more about the first stars and galaxies, consider the Universe as a Superset consisting of every possible matter and space you could think of. The universe as we know it today was not even close to what it is back roughly 13.8 Billion years ago.
To know about the formation of the first stars and galaxies let’s know about its origin. The birth of the universe is a subject that has mesmerized scientists, philosophers, and theologians for centuries. The winning scientific description for the origins of the universe is known as the term Big Bang theory. The big bang played is the crux for the formation of the first stars and galaxies. According to this concept, the universe originated as a distinct element, a point of unbounded density and temperature, about 13.8 billion years prior. In this article, we will discover the scientific proofs and theories that support the Big Bang theory and the subsequent evolution of the universe.
1.1 Big Bang Theory
To know more about the formation of the first stars and galaxies let us know about the big bang theory. The prime evidence for the Big Bang theory came from observations of cosmic microwave background radiation. Earlier back in 1960s, scientists Arno Penzias and Robert Wilson discovered a low-level noise that is believed to come omnidirectional in the sky. This noise was eventually identified as the afterglow of the Big Bang, a faded radiation left over from the moment the universe first became translucent, about 380,000 years later after the Big Bang.
Another key piece of proof for the Big Bang theory is the observed plenty of lighter elements namely hydrogen, and helium, in the universe. These elements are thought to have been formed in the first few minutes after the Big Bang, during a process known as nucleosynthesis. The observed abundance of these elements matches the predictions of the Big Bang theory, providing further support for the model.
The extension of the universe is another key part of the Big Bang theory. According to this model, the universe is still expanding, with distant galaxies moving away from us at increasing speeds. This expansion is thought to have started shortly after the Big Bang and is believed to be caused by the energy of the universe itself.
1.2 More About The Big Bang
Our Universe was formed after the explosion of Space. Before Big Bang, our universe was just a small dot-like entity(Dark Matter) that gradually started expanding and then simply burst because it started getting denser and denser and its temperature started rising gradually making it pop. This is necessary for the formation of the first stars and galaxies. To make it easy to understand consider our universe like a bubble, the air inside bubble was more than it could hold and the rise of its temperature is the main reason for its explosion. This theory was coined as “Big Bang Theory”.
In my Bubble example above, consider the bubble as our universe and the air blown inside as space. After the explosion of the Universe, it slowly and gradually started cooling off. But things weren’t the same as before now many reactions between matters started happening in tandem. The space after the Big Bang started expanding and it’s still expanding and would be ever-expanding. Currently, the diameter of the universe that we could roughly notice is 4.40 x 1023 km.
Many reactions lead to the expansion of the universe like the formation of the first stars and galaxies. So to conclude, It’s been a billion years and our universe is still expanding. There are still ongoing reactions taking place somewhere in the universe that we are not aware of. Now that we have some Idea about how the universe was formed and how it works, we must move ahead with how the early stars were formed.
2. Early Stars (Very First stars)
Stars like Sun didn’t appear for over 100 million years even after the big bang theory. It is believed that the phenomenon of early star formation took a significant time to make its first appearance in cosmic history. Back then, it was difficult or nearly impossible to observe the stars naturally due to the lack of proper equipment like a good telescope. It took years of study and research to develop the Hubble space telescope and James Webb telescope that could be used to observe and study the cosmic world.
Back then, cosmologists used to figure it out using cosmic microwave background radiation. Stars are massive, luminous bodies that are responsible for generating light and heat, and are the building blocks of the cosmos. But how did they form, and what factors contributed to their evolution? In this essay, we will explore the formation of stars and galaxies, and the processes that shaped them.
The formation of stars was mainly believed to be a cluster of clumps that later developed into gravitational bounded shape and later formed a bigger clump by the amalgamation of similar structures with itself. These structures would later form protogalaxies ending up with a galaxy. These early stars or very first stars were known to have been born way earlier than even the Earth itself. They were known as Population III stars.
3. Population III Stars
The formation of stars and galaxies starts gradually. The birth of any star begins with giant molecular clouds formed by Dust and Gas. These vast molecular clouds are also known as “Nebulae” or “Dark Nebulae”. The word “Nebula” is a Latin term that in English translates into Mist. These vast molecular clouds comprise mainly hydrogen and helium particles as major ones and other constituents as minor.
For the formation of the first stars and galaxies let’s learn about Population III stars. Population III stars, also known as primordial stars, are believed to be the first stars that developed in the universe later after the Big Bang. These stars are thought to have formed from clouds of hydrogen atoms and helium gas that were present in the early universe, before the formation of galaxies and other structures.
3.1 Formation Of Population III Stars
The Population III stars concept was first proposed in the 1970s, and since then, multiple amounts of observational and theoretical studies have been carried out to understand these objects better. Despite their importance in the early universe, Population III stars have never been directly observed because they are thought to have died out long ago.
One of the key properties of Population III stars is their chemical composition. These stars are thought to have formed from gas clouds that consist of only hydrogen, helium, and very minute amounts of lithium. The absence of heavier elements in these clouds is because heavier elements are formed in stars through nuclear fusion reactions and are released into the interstellar medium when the star dies in a supernova explosion.
As such, the earliest stars had no such source of heavy elements and were born with only the light elements that existed in the early universe.
3.2 Life Span And Other Characteristics
On the discovery of the first stars, astronomers had originally classified them into two types of stars. The classification was based on the availability of the metal elements that were observed in the stars. The stars were originally classified into two types 1. Population I stars and Population II stars
Population I stars consisted of traces of heavy amounts of metal elements. Due to this phenomenon, they were as known as metal-rich stars. They consisted of heavy amounts of a trace of metal elements which were heavier than helium. On the contrary, there were population II stars. These stars were also termed metal-poor stars as they consisted of a lesser amount of metal present in them. Later it was revealed that even the metal-poor stars consisted more of metals than gas so they later classified the stars and a third type was founded ie. Population III stars.
The population III stars were mainly consisting of primordial gas like hydrogen and helium with very little trace of lithium and beryllium. These stars vary mainly rich in gases and are formed majorly of gases. This also concluded that the Population III star’s metal elements did not consist of any old and recycled material but the remnants of the Big Bang itself. This phenomenon made Population III stars unique on their own. The life span of any star depends upon its size, the bigger they are the more energy it would require to produce and due to this the more early they die, however, in general stars can last about a few million to 15 billion years.
These stars were also considered the first stars of their generation because of the fact that no recycled element of the previous gen was present in them. However, it is presumed that during the later stages, even the population III stars would have the presence of metals and increase their metallicity. Currently, no population III stars are observed and therefore they remain as hypothetical elements in the world of the cosmos.
3.3 Formation Of Population III Stars
While they have never been directly observed, their existence is supported by several lines of evidence, and they continue to be the subject of intense theoretical and observational study. Ideally, these molecular clouds are ice-cold and stable. However, in the event of any nearby supernova, a large wave of shockwave could pass through the molecular cloud. These shockwaves could carry a tremendous amount of energy with them. The supermassive energy could disturb the gravitational field of the molecular clouds which in turn results in the collapse of the cloud by itself by making hydrogen and helium molecules come together very close making them dense.
This phenomenon leads to an increase in the mass and the gravitational pull leading to the pulling of more hydrogen and helium atoms nearby the molecular cloud. As more molecules start gathering in the central part of the core of the clouds and start heating up, this core is also known as “Protostar”. The Protostar begins raising its temperature by pulling in more and more hydrogen atoms, helium atoms, and other molecules.
This temperature keeps on rising and goes to the extent where the hydrogen nuclei begin fusing with themselves releasing helium and light, heat, and radiation. This procedure is termed nuclear fusion. During this phenomenon, the inward force of gravity is in exact ratio to that of outward gravitational pull. This delicate gravitation leads to the birth of a new star. The inward and outward balance keeps the star alive for several thousand to billion years. Until finally it dies.
4. The Death Of A Star
Every form of the life cycle begins and inevitably has to die. The life cycle plays a critical role in the formation of the first stars and galaxies. The stars are no exception. The death of the star begins when it becomes unable to produce more hydrogen for nuclear fusion. The moment the star fails to maintain the hydrogen for its fusion the inward pressure starts exerting itself on the star shrinking it from the original size it was due to its own gravitational pull. The compression leads to the development of a small star.
This small star starts the nuclear fusion process again. This time, nuclear fusion would produce helium and other heavier elements from the periodic table up to Iron. Soon the white dwarf depending on its original size transitions into a red giant or a super red giant by expanding itself again due to nuclear fusion. If the start transforms into a red giant then after a short time it again becomes unstable and expels its out layering containing all the dust and gas and shrunk forming a White dwarf. This is a part that leads to the formation of the first stars and galaxies
This white dwarf is a hot and dense compressed. Over a course of time, this white dwarf becomes cooler and gets darker. Finally, it transitions into a black dwarf since it’s out of energy to do any nuclear fusion. On the other hand, if it was a super red giant it would have transitioned into a star again and then exploded forming a supernova.
5. The Formation Of Galaxies
Stars are born from clouds of gas and dust, Similarly, galaxies are born from clouds of stars. The contemporary leading theory of galaxy formation is the hierarchical model, which hypothesizes that galaxies are formed through a process of mergers. A galaxy is a vast structure of stars, gas, dust, and dark matter that is compiled together by gravity.
Galaxies are observed in various shapes and sizes, ranging from small, irregularly shaped dwarf galaxies with a few million stars to giant elliptical galaxies with trillions of stars. Our galaxy, the Milky Way, is a type of spiral galaxy that is estimated to consist of around 100 billion stars. It is just one of the billions of galaxies in the noticeable universe and is situated in a group of galaxies known as the Local Group. This is a factor in the formation of the first stars and galaxies.
Galaxies can be categorized into mainly three types based on their shape: spiral, elliptical, and irregular. Spiral galaxies have a flattened disc shape with spiral arms that extend outwards from a central bulge. Elliptical galaxies, on the other side, have a much spherical or elongated shape and contain mostly older stars. Irregular galaxies have no particular shape and are characterized by their chaotic appearance.
5.1 Formation Of Galaxies
The formation of galaxies consists of the fusion of clouds of gases and dust held together by the gravitational field. Edwin Hubble made a classification of galaxies based on the tuning fork diagram. They consist of three types that are spiral, elliptical, and irregular. The spiral galaxies are the ones that appear flat disc-shaped with yellowish bulges in their center. The spiral galaxies are further classified into two groups normal spirals and barred spirals.
In spiral galaxies are furthermore classification was made based on the shape and magnitude of their central bulge along with the texture of their arms. Our galaxy ie. The milky way is a barred spiral galaxy. The next kind of galaxy is an elliptical one. This type of galaxy is shaped from near-to circular to elongated. The types of galaxies consist of one-third of the population in the cosmos.
Elliptical galaxies consist of stars that are very older or mostly about to die. Due to this phenomenon, their ability to produce energy and gravitational pull starts to cease due to which the shape of these galaxies becomes elongated. The last classification of the galaxy is the irregular type. There are types of galaxies that are majorly found throughout our cosmos.
These types of galaxies consist of no fixed shape or size. These types of galaxies are majorly formed through the collision of other stars and galaxies or any other violent activity among them. Irregular galaxies are older than the spiral and elliptical types of galaxies and are found majorly in our universe.
5.2 Connection With Big Bang Theory
The big bang is the reason for the expansion of the universe. The big bang played are crucial role in the formation of the first stars and galaxies, it was because of the big bang that not only our galaxy but other galaxies developed. During the big bang, a lot of energy and heat was released with the particles spreading all across the universe. These particles consisted of clouds of dust and gases. Later these clouds of dust came together and formed stars.
These stars had their own gravitational field and the energy to survive. The energy they got was majorly from hydrogen fission this energy produced a huge amount of heat and gravitational pull. Similar to the formation of stars our planet started forming from clouds of gases and dust.
Due to the gravitational pull from the stars, the planets are revolving in their respective orbit. If the big bang had not occurred we would have never existed in the very first place. Even now there is an ongoing process of the formation of new stars and galaxies across our universe. Our universe is ever-expanding. However, most of the elements are still unknown to us humans. These elements can’t be observed under light. Such elements or matter are known as Dark Matter.
Our Universe consists majorly of Dark matter. Their purpose is still unknown to the scientists and ongoing research and study are still going on. The continuous production of heat leads to the formation, collision, and death of galaxies across the universe. This is vital because heat and energy are a vital part of our existence and a reaction. In order to keep the reaction in action, the heat and energy must find a way to produce themselves. This is how the survival of our universe is made possible.
6. Conclusion
To conclude, The Big Bang plays are very crucial role in the existence of our universe without the big bang our universe couldn’t exist in the very first place. The formation of the first stars and galaxies is only possible due to the big bang. The stars and galaxies are surviving due to the ability to continuously produce the energy to survive. With the sun produces enough energy to keep the planets together in their orbits and planets have enough energy to keep themselves revolving around and nourishing themselves. Every entity in the universe plays a very crucial role in the formation of the first stars and galaxies.
The expansion of the universe will be ongoing, going through the different stages is a very important part of this life cycle. Scientists still believe that we have only discovered a very small part of our universe and there are many more truths and facts which are yet to be discovered by our universe. There are many dark unknown places to be discovered and many other truths to learn.
Last Updated on by Sathi