How the Very First Galaxies Were Born?

I am ready to write this article for your space website. The topic of how the very first galaxies were born is a fundamental and awe-inspiring question in astronomy, and I can explain the current scientific understanding in a simple and accessible way.

The First Lights: How the Very First Galaxies Were Born

When you look up at the night sky, you see a universe full of galaxies. Our own Milky Way is just one of billions of huge island cities of stars, gas, and dust. But where did they all come from? The universe was not always full of these beautiful, swirling galaxies. It started as a dark, empty place. The story of how the very first galaxies were born is a story of incredible cosmic change, from a smooth, hot beginning to a universe that was a “cosmic web” of stars.

This story takes us back to a time when the universe was just a baby, only a few hundred million years old. It is a story that involves a mysterious, invisible substance called dark matter, the formation of the very first stars, and a process of cosmic growth that continues even today. In this article, we will explore how scientists believe the first galaxies were born, what their role was in lighting up the universe, and how a powerful new telescope is helping us see them for the very first time.

The Universe’s Beginning: A Hot and Dark Time

Our story begins almost 14 billion years ago with the Big Bang. For the first few hundred thousand years, the universe was an incredibly hot and dense place. It was like a thick, hot soup of protons, electrons, and light. The light was constantly bumping into the free-floating electrons, so it could not travel freely. The universe was completely opaque, and there were no stars or galaxies.

After about 380,000 years, the universe had expanded and cooled down enough for the electrons to be captured by the protons. They formed the first simple atoms of hydrogen and helium. This was a huge moment for the universe. The “fog lifted,” and light was finally free to travel. This ancient light is what we see today as the Cosmic Microwave Background.

But after this moment, the universe entered a period that scientists call the “cosmic dark ages.” The universe was filled with a simple gas of hydrogen and helium, but there were no stars to light it up. The universe was dark and mostly empty.

The Invisible Architect: Dark Matter’s Crucial Role

To get from a dark, empty universe to a universe full of galaxies, something had to pull the gas together. That something was dark matter. Scientists believe dark matter is a strange, invisible substance that makes up most of the matter in the universe. It doesn’t give off any light, but it has a very powerful gravitational pull.

In the early universe, this invisible dark matter was not perfectly smooth. It had tiny clumps and knots. The gravity of these dark matter clumps was what first pulled the normal gas of hydrogen and helium together. It acted like a kind of “cosmic scaffolding,” a giant invisible structure that began to pull all the normal matter into it. Without the gravity of this dark matter, the first galaxies would never have been able to form.

The First Stars: The Universe’s Light Switch

As the dark matter clumps got bigger and bigger, they pulled in more and more gas. In the densest parts of these clumps, gravity squeezed the gas so hard that it became incredibly hot. Eventually, the center of these clumps became so hot that nuclear fusion started. This is the process that makes a star shine. The very first stars in the universe were born inside these dark matter clumps.

These first stars were much different from our Sun. They were much bigger and brighter, and they were made of only hydrogen and helium, as heavier elements had not yet been created. These stars burned through their fuel very quickly and lived for only a few million years before they died in a massive supernova explosion. These explosions were the first to scatter heavier elements into the universe. The light from these first stars ended the cosmic dark ages and began the process of “reionization,” where the light from the stars broke apart the neutral hydrogen gas in the universe.

The First Galaxies: Cosmic Clouds and Mergers

The first galaxies were not born all at once. They were born from the continued growth of the dark matter clumps and the stars inside them. As the first stars were born and died, their gravity pulled in more and more gas. The stars also gathered together in small groups. These groups of stars were the very first, tiny galaxies, also called protogalaxies. They were much smaller than our own galaxy, the Milky Way, and they were more like small, fuzzy blobs.

The early universe was a very busy place, with billions of these small, fuzzy galaxies. The gravity of these galaxies pulled on each other, and they began to collide and merge. This process of merging was how the first galaxies grew bigger and bigger. They were like cosmic clouds that were constantly merging to create a bigger, more complex cloud. Over billions of years, these mergers led to the formation of the huge, beautiful spiral and elliptical galaxies that we see today. The very first galaxies were the building blocks of the entire universe.

The Cosmic Web: A Giant Network of Galaxies

If you could see the entire universe at once, you would see that the galaxies are not scattered randomly. They are arranged in a huge, beautiful, and intricate pattern called the cosmic web. The cosmic web is a network of long, thread-like strings of galaxies, called filaments, and huge, empty spaces called voids. The galaxies and galaxy clusters are located in the filaments, which connect the entire universe together.

This structure was first built by the gravity of dark matter. The filaments are the places where the dark matter was the most dense, and the voids are the places where the dark matter was the least dense. The gravity of the dark matter pulled all the normal matter into the filaments, which is why all the galaxies are located there. The cosmic web is a testament to the power of dark matter’s gravity.

Our Eyes on the Past: The James Webb Space Telescope

For a long time, the first galaxies were just a theory. They were too far away and too dim for our telescopes to see. The light from these galaxies has been traveling for more than 13 billion years, and it has been stretched by the expansion of the universe. By the time the light gets to us, it has become infrared light, which is invisible to our eyes.

Now, we have a new and very powerful telescope that can see in infrared light: the James Webb Space Telescope (JWST). The James Webb is giving us our first look at the very first galaxies. It is seeing light from a time when the universe was just a few hundred million years old. The images from the James Webb are showing us that the first galaxies were much more active and much more complex than we had ever thought. The telescope is giving us a new picture of the early universe and is helping us to better understand how all the stars and galaxies we see today came to be.

Conclusion

The story of the first galaxies is a beautiful and complex one. It began in a dark, empty universe and was first built by the gravity of dark matter. The first stars were born, and their light ended the cosmic dark ages. The first galaxies were born from a process of cosmic mergers, where small, fuzzy blobs of stars came together to form bigger galaxies. The result is the huge, beautiful, and intricate cosmic web that we see today. The James Webb Space Telescope is now giving us our first look at these first lights, and it is helping us to write a new chapter in our understanding of the universe. The story of our cosmic home is a story of how a universe of darkness became a universe of light.