As a kid you must have learnt that the Sun, Earth and all other planets that we see in our solar system reside in a galaxy called The Milky Way. At that age, you might not have questioned what exactly a galaxy is or how it was formed. Although, now that we’ve grown up, let’s try to fulfill that curiosity. Why should we limit the topic to the community of astronomers and astrophysicists, right?
The term ‘galaxy’ comes from the ancient Greek work ‘gala’. It means a stream of milk flowing through the sky. This was a reference to what sub Saharan African natives gazed upon at night in the sky. The Milky Way galaxy is a collection of stars, cosmic dust, planets, asteroids and many other interstellar entities. It is a spiral galaxy and has been continuously expanding like the rest of the universe since its creation.
But how old is the Milky Way galaxy? What was the reason behind its creation? These are some questions that a lot of people have in their minds. Now let’s start discovering the secrets of this galaxy and ultimately start to find the answer to such questions.
The History of the Milky Way Galaxy: To The Early Days
When astronomers looked back in time, they found out that the Milky Way galaxy was formed about 14 billion years ago when clouds of gasses after the inception of universe started to come together under the action of gravity. As the gasses cooled down, they started to turn into different states and form different celestial objects like stars. During this time, everything in our galaxy was randomly floating in the universe and there was no sign of the solar system either.
With time, two structures, a spherical ‘halo’ and then a dense bright disk appeared in the cosmos after the universe cooled down followed by accumulation of gasses and particles. Now you might be thinking how did these gasses change their state and form such a huge galaxy? Well that answer can only be obtained through chemistry and the study of various chemical reactions.
In terms of physics, the change of states happened due to transfer of heat and other thermodynamic processes. In astronomical terms, a million years is just like a few minutes and that is why the early days that we talk about here are actually millions and millions of years that the Milky Way galaxy took to finally take a shape.
Talking about the history of the Milky Way galaxy, one can’t help but wonder if there are other planets out there that support life? The Milky Way is certainly massive. It’s a statistical improbability to imagine that we are the only ones out here. Luckily, there are a lot of exoplanets out there that we can study, which could be the key to finding life beyond our own solar system. Learn more about these fascinating exoplanets here.
The Formation
The shape of the Milky Way galaxy is just like a spiral with multiple star systems, like the solar system, residing on its spiral arms. But the galaxy did not just come together in this shape initially. During the ‘baby phase’ of the galaxy, stars were formed only of hydrogen and helium, which are the rawest elements of the universe.
These stars gave rise to multiple celestial objects too because of their strong gravity. A lot of these stars are still burning and giving out light and spiral motion to the galaxy. When we look up at the sky today, what we are seeing is the galactic equivalent of Rome. It is so because the Milky Way galaxy is a metropolis of stars with multiple layers of history still left to unravel.
Satellites have shown that as soon as the universe started to cool down, it became kind of transparent. There are traces of development of hydrogen atoms for the first time during this period.
These basic atoms would have been used up in the formation of earliest black holes and complete galaxies. The initial formation of the Milky Way galaxy was due to the metal poor stars. There were about five thousand ancient stars out of which roughly about 42 have become permanent citizens of the inner disk of our galaxy.
A Violent Youth
Sure, the history of the Milky Way galaxy involves it starting out as nothing and slowly budding and taking the shape of what it is now. But there is also another addition to the story.
Hemer Koppelman, an astronomer at Institute for Advanced Study in Princeton, used Gaia data set to reveal the presence of debris from one of the largest mergers in the center of the Milky Way galaxy. In the center of the galaxy, he could see that there were a large number of halo stars that showed ping pong motion back and forth. The only explanation possible for such a cluster was a merger with a dwarf galaxy in the earlier times. They even published a research paper which stated this violent youth of the Milky Way galaxy.
The Milky Way galaxy’s shape is spiral because of this merger as roughly about all of the stars in the inner 60,000 light years of the halo of this galaxy are said to have come from this collision itself. This merger contributed to about a 10 percent increase in the mass of the Milky Way galaxy.
The astronomers named the dwarf galaxy Gaia-Enceladus and the reason behind having a thin and thick disk in the spiral of our galaxy is cleared with the explanation of this merger. The collision between the two galaxies took place about ten billion years ago and destroyed the first central disk of our galaxy. This swept away most of the star clusters and thus gave rise to thin and thick disks in our galactic plate.
As you immerse yourself in the captivating history of our Milky Way galaxy, ask yourself if you’ve wondered about the potential of colonizing other planets? If you have, we’ve put together a comprehensive step-by-step guide to planet colonization. It’s a fascinating read that will leave you inspired and intrigued about the future that lies ahead.
The History of the Milky Way Galaxy is Fascinating
It’s clear that the history of the Milky Way galaxy is full of twists and turns. There are still a lot of things that are to be understood about this galaxy, though. The Hubble Space Telescope in space is collecting data, looking deep into the history of the galaxy, up to as long as 13 billion years in the past.
Even today, researchers have found out that two dwarf galaxies, Small and Large Magellanic Clouds, are rushing towards the Milky Way galaxy and it seems like the collision is inevitable. But this is not going to happen in this lifetime of yours. It will still be millions of years before such an incident occurs and reshapes the Milky Way galaxy. For now, you should keep your mind open to all the various possibilities of formation of the Milky Way galaxy.
Scientists are yet to discover the dark age before the formation of any galaxy to see what was there back then. The answer of when was the Milky Way galaxy first discovered and what shaped it is also still left to be answered completely. There is a lot more that humans do not know about this galaxy.