Universe of Galaxies: Cities of Stars

Just imagine.

The Universe of Galaxies: Cities of Stars. Enormous, furious megalopolises where billions of stars glow like windows in skyscrapers, and planets are small apartments where, perhaps, someone lives. The distances between these “cities” are so huge that even light moving at incredible speed needs millions of years to cover them. And among these cities there are real giants – galaxies, striking in their size, mass and beauty. Let’s talk about them.

What makes a galaxy “big”?

The first question that may arise is: what does a “large galaxy” even mean? It’s not just the number of stars, although that plays a role. Imagine the diameter of the galaxy, its mass, the amount of dark matter that holds it all together like an invisible framework. For example, our galaxy, the Milky Way, seems huge to us. Its diameter is about 100,000 light years. But on a cosmic scale, it’s only average. There are galaxies that are dozens of times larger. And that’s where the real magic begins.

Why do some galaxies become giants while others remain small? Often it’s a matter of merging. Imagine two galaxies gradually drawn closer together by gravity. They merge to create something much larger. Sometimes this process takes billions of years, but the results are worth it. And then there’s dark matter, a mysterious substance we can’t see but that affects everything around us. It’s what helps galaxies grow and hold their shape.

IC 1101: A Stunning Galaxy

One of the largest galaxies we know of is IC 1101. Its size is simply incredible: its diameter is about 6 million light years. That’s 50 times larger than the Milky Way! Imagine if it took the place of our galaxy. Its edges would extend all the way to the neighboring Andromeda galaxy, which is 2.5 million light years away. And that’s just one of its records.

IC 1101 contains about 100 trillion stars. This number is so large that it is difficult to imagine. For comparison: there are “only” 200-400 billion of them in the Milky Way. And this galaxy is at an incredible distance from us – more than a billion light years. This means that the light we see today was sent to us at a time when there were no dinosaurs on Earth.

ESO 306-17: The Predator Galaxy

If IC 1101 amazes with its size, then ESO 306-17 amazes with its character. This galaxy is a real predator. It swallows its neighbors, increasing in size and mass. Imagine a huge web, gradually drawing in everyone who is nearby. This is how ESO 306-17 became one of the largest galaxies in the Universe.

But there is another curious detail. After a galaxy absorbs its neighbors, a void forms around it – a huge space where there are almost no other galaxies. This is similar to how large cities “suck” resources from the surrounding villages. Only on a cosmic scale.

UGC 2885: The Quiet Giant

Not all great galaxies are violent. Here is UGC 2885, a galaxy that is impressive in size, but also calm and composed. It is about 800,000 light years across, making it one of the largest spiral galaxies we know of.

Why is it so big, but not “hunting” its neighbors? Astronomers believe that it is simply located in an empty region of the Universe, where there are not many other galaxies. Therefore, it grows slowly, without stress and conflict. You could say that it is a galaxy enjoying life.

Messier 87: A Galaxy with a Supermassive Black Hole

If you’ve heard about the first photo of a black hole taken in 2019, then you’re already familiar with Messier 87. This galaxy is famous not only for its size, but also for the supermassive black hole at its center. The mass of this hole is about 6.5 billion times that of our  Sun.  Hard to imagine, right?

Messier 87 is also a galaxy that constantly shoots out jets of plasma for thousands of light years. It resembles a huge cosmic fountain that has been working for millions of years. And although the galaxy itself is not the largest, its activity makes it one of the most interesting.

NGC 6872: A Galaxy with Long Arms

And finally, NGC 6872 is a galaxy that is striking in its structure. Its spiral arms stretch for hundreds of thousands of light years, making it one of the largest spiral galaxies in the Universe. But why is it so big? All because of its neighbor, a smaller galaxy that, as it passed by, stretched its arms with its gravity. It resembles a dance, where one partner literally “directs” the movements of the other.

How are giant galaxies born?

To understand how monsters like IC 1101 or ESO 306-17 come into being, we need to look into the universe’s past. Imagine the early  space, billions of years ago. Galaxies were smaller then, but there were many more of them. They were constantly colliding, merging, and growing, like cities gradually merging into megalopolises. One of the most interesting processes is galaxy mergers. Imagine two galaxies slowly moving toward each other under the influence of gravity.

At first they just “touch” the edges, but then their stars, gas and dust begin to intertwine. It’s like a dance, where each movement creates new shapes. Eventually they merge into one big galaxy. Sometimes this is even accompanied by explosions of new stars that flare up like fireworks. But not all galaxies become big because of merging. Some, like UGC 2885, simply grow slowly, devouring gas from the surrounding space. It’s like a tree that gradually grows from small seeds. Others, like ESO 306-17, become giants by “eating” their neighbors. It’s like in the natural world: some live peacefully, and some are predators.

Dark Matter: The Invisible Framework of the Universe

Another key element in the formation of large galaxies is dark matter. We can’t see it or feel it, but it’s there. Dark matter is like an invisible framework that holds galaxies together. Without it, they would simply fly apart under their own gravity. Think of a galaxy as a city, and dark matter as its foundation. The more of this foundation, the larger the city can become. That’s why large galaxies like IC 1101 have such huge “reservoirs” of dark matter. It helps them hold their shape and grow.

Record-Breaking Galaxies: Not Just in Size

When we talk about large galaxies, of course, the first thing that comes to mind is their size. But there are galaxies in the Universe that amaze us with other characteristics. Here are some examples:  The brightest galaxy  : WISE J224607.57-052635.0. This galaxy shines 350 trillion times brighter than our  Sun.  Imagine if it were next to us, we would simply not be able to look at the sky without sunglasses.

• Oldest Galaxy  : GN-z11. This galaxy is 13.4 billion light years away. This means that we see it as it was only 400 million years after the Big Bang. It’s like looking into the Universe’s ancient past.
• The most active galaxy  : quasars. These are galaxies with supermassive black holes in the center that emit incredible amounts of energy. For example, quasar 3C 273 shines 4 trillion times brighter than our  Sun.  It is so bright that it can be seen even in an amateur telescope.
• The most amazing galaxies  : galaxies with unusual shapes. For example, the Ceitinhan Galaxy (Sombrero Galaxy) resembles a Mexican hat, and the Carina Galaxy (Cartwheel Galaxy) looks like a wheel rolling  through space  .

Comparison of the sizes of the largest galaxies with the Milky Way:

Galaxy	Type	Diameter (light years)	Number of stars	Interesting feature
Milky Way	Spiral	~105 000	~200–400 billion	It has satellite galaxies and is approaching Andromeda.
IC 1101	Giant Elliptical	~6 000 000	~100 trillion	The most famous galaxy, 50 times larger than the Milky Way
ESO 306-17	Elliptical	~1 000 000	Unknown	Surrounded by traces of absorbed galaxies
UGC 2885	Spiral	~800 000	~1 trillion	It is considered the largest spiral galaxy.
Messier 87	Elliptical	~980 000	~2.7 trillion	Has a supermassive black hole, famous for the first photo of a black hole (2019)
NGC 6872	Spiral	~522 000	Unknown	The longest spiral arms in the known universe

How do we study these giants?

Modern science allows us to look into the most distant corners of the Universe. Instruments such as the Hubble or James Webb telescopes allow us to see galaxies that are billions of light years away. But how does it work? Imagine that light is a letter that takes billions of years to reach us. When we see a galaxy that is a billion light years away, we are actually looking into the past. It is like a time machine that allows us to see what the Universe looked like in ancient times. And then there are radio telescopes such as ALMA, which allow us to study galaxies through radio waves. This is especially useful for galaxies that are hidden behind clouds of cosmic dust.

What lies at the center of large galaxies?

If galaxies are cities, then their centers are the true hearts of these megalopolises. And, like any city, this is where the most dramatic events take place. At the center of most large galaxies are supermassive black holes. They are so large that their mass can be billions of times greater than that of our  Sun.  And they don’t just sit there — they actively influence everything around them.

For example, in the center of the galaxy Messier 87, which we have already mentioned, there is one of the most famous black holes. Its mass is about 6.5 billion solar masses. But the most interesting thing is that it is constantly feeding on matter from the surrounding space. When gas and dust fall into the black hole, they heat up to incredible temperatures and begin to glow. This creates bright jets of plasma that shoot out thousands of light years into  space  . Imagine a huge cosmic fountain that has been working for millions of years!

But black holes aren’t just destroyers. They also play a key role in the formation of galaxies. For example, their gravity helps hold stars in place, and the energy released as they “eat” matter can stimulate the birth of new stars. It’s like the cycle of nature: something dies to give birth to something new.

Vanishing Galaxies

One of the biggest mysteries of the Universe is that some galaxies disappear. No, they do not explode or disintegrate. They simply become invisible to us. This happens because the Universe is expanding, and distant galaxies are moving away from us at incredible speeds. Therefore, their light is “stretched” and goes into a range invisible to our eyes.

For example, the galaxy GN-z11, which we have already mentioned, is at the edge of our observation range. In a few million years, it will completely disappear from our field of view. This reminds us that the Universe is not something static. It is constantly changing, and we can only see a small part of this huge puzzle.

How do large galaxies affect their neighbors?

Large galaxies like IC 1101 or ESO 306-17 don’t just exist in isolation. They actively influence their neighbors. For example, the gravity of a large galaxy can “pull” stars and gas out of smaller galaxies that are nearby. This is similar to how large cities “suck” resources out of the surrounding villages.

But sometimes this influence can be more dramatic. Large galaxies can literally “tear” their neighbors to shreds. For example, the galaxy NGC 4038, which is in the process of merging with the galaxy NGC 4039, creates huge waves of gas and dust that fly away for thousands of light years. It resembles a cosmic dance, where every movement leaves a trace in space.

Ghost Galaxies

There are also galaxies that are called “ghosts.” They contain almost no stars, but have a lot of dark matter. For example, the galaxy Dragonfly 44, which is located in the constellation Coma Berenices, is almost invisible because it consists mainly of dark matter. It has a mass of about a trillion solar masses, but very few stars.

Such galaxies are real mysteries for astronomers. They remind us that there is still much we do not know about the Universe. And perhaps they hold the keys to understanding dark matter and its role in the formation of galaxies.

Why is studying large galaxies important?

Studying large galaxies is not only a way to satisfy our curiosity. It is also the key to understanding how the universe formed and how it functions. For example, by studying galaxies, we can understand how dark matter influences their structure, how black holes shape their evolution, and how merging galaxies create new forms of life.

In addition, large galaxies are unique “laboratories” for studying physical laws. For example, observing galaxies helps us better understand how gravity works, how stars form, and how matter evolves.

What does the future hold for us?

Our knowledge of the Universe is constantly growing. New telescopes, such as the James Webb, allow us to look even further into  space  and see galaxies that were previously inaccessible to observation. It may be that soon we will discover new giant galaxies that will amaze us with their size and properties.

But the most interesting thing is that each new discovery poses new questions. For example, are there galaxies that are even larger than IC 1101? Can galaxies “die” and how does this happen? And, most importantly, is there life in these huge cities of stars?

Chameleon Galaxies: How They Change Over Time

One of the most interesting features of galaxies is their ability to change. Imagine that a galaxy is a living organism that has been evolving for billions of years. It can change its shape, color, and even behavior. For example, some galaxies, once spiral, become elliptical due to merging with other galaxies. This is reminiscent of the metamorphosis that occurs in nature when a caterpillar turns into a butterfly.

But there are other examples. Some galaxies, once active, eventually “fall asleep.” Their black holes stop “feeding” on gas, and the galaxy becomes quieter. Others, on the contrary, “wake up” after millions of years of rest. For example, the galaxy NGC 5128, also known as Centaurus A, was once an ordinary elliptical galaxy. But after merging with a smaller galaxy, it became one of the most active galaxies in our region of the Universe.

Galaxies that are “dying”

Not all galaxies have a happy fate. Some of them “die”, that is, they stop giving birth to new stars. This happens because they lose their gas, which is the main fuel for star formation. For example, the galaxy MACS 2129-1, which is 10 billion light years away from us, is already practically “dead”. It stopped creating new stars billions of years ago, and now it is inhabited only by old, cold stars.

But even “dead” galaxies can be interesting. They remind us that everything in the Universe has its end. And perhaps one day our galaxy, the Milky Way, will also stop its life.

Galaxies that challenge our understanding

There are galaxies in the universe that defy our understanding of physics. For example, the galaxy NGC 1277, which is 220 million light years away, has a supermassive black hole that makes up almost 14% of its total mass. This is incredibly large when you consider that in most galaxies, the black hole makes up only 0.1% of the mass.

Or the galaxy NGC 1052-DF2, which has virtually no dark matter. This contradicts our understanding of how galaxies form, since dark matter is considered their main framework. Such galaxies remind us that the Universe always knows how to surprise.

Galaxies that “run away”

There are also galaxies that move at incredible speeds. For example, the galaxy EGSY8p7, which is 13.2 billion light years away, is moving at a speed that is almost equal to the speed of light. This is because the universe is expanding, and distant galaxies are moving away from us at incredible speeds.

But there are other examples. Some galaxies “escape” because of collisions with other galaxies. For example, the galaxy NGC 4522, located in the Virgo cluster, is moving at a speed of more than 10 million kilometers per hour because it was “pushed” by other galaxies.

Inspiring Galaxies

Large galaxies are not only objects of scientific study. They also inspire us with their beauty and grandeur. For example, the Whirlpool Galaxy (M51), which is 23 million light years away, amazes with its spiral arms, reminiscent of a huge cosmic vortex. And the Sombrero Galaxy (M104) amazes with its unique appearance, reminiscent of a Mexican hat.

These galaxies remind us that the universe is not only a place for scientific exploration, but also a source of inspiration. They inspire artists, writers, and even philosophers to reflect on the place of humans in the universe.

The universe is a never-ending story

Large galaxies are just one of many pages in the vast book of the Universe. They remind us of how vast and diverse our world is. And although there is much we still do not know, it is precisely this unknown that makes  space  so fascinating.

So next time you look up at the night sky, think: every star you see is just a tiny part of a huge city called a galaxy. And there are billions of such cities in the universe. And each of them has its own history, its own mystery, and its own beauty.

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