[비즈한국] There is a work that made Maurizio Cattelan, known as “the heretic of the world of modern art”, even more famous. It’s “banana”. An artwork with yellow bananas attached to a white wall with tape. I wonder if it’s a work of art, but surprisingly it’s a 100 million won banana. This work became even more famous when another artist, who came as a visitor, removed the banana and ate it. As the title of the work “Comico” suggests, these are stories that will make you laugh.
But recently in the world of astronomy an interesting discovery like this banana occurred. The title of the article is in bold. “Galaxies go crazy!” It’s a play on words meaning that the galaxies are turning into bananas, or that the galaxies have gone crazy. This article contains the discovery that the primordial galaxies of the universe identified by James Webb do not have the shape familiar to us, but have a strange shape bent like one. banana. Literally, the further into the past you go, the more bananas the galaxies become! Spiral galaxies, elliptical galaxies and now banana galaxies. Let’s dive into the past of galaxies of various appearances.
Let’s talk about the identity of the strange primitive banana-shaped galaxies (?) discovered at the edge of the universe.
There’s a question I often get asked about the shape of galaxies. “Gravity acts in all directions, so why is our galaxy shaped like a flat disk?”
Most of the beautifully swirling galaxies we know, such as the Milky Way and the Andromeda Galaxy, are flat disk galaxies. In addition, there are elliptical galaxies in which stars are scattered and collected in a round shape. At first glance, an elliptical galaxy with stars gathered in a circle looks much more natural. Flat disk galaxies are difficult to understand at first glance. But we need to take the opposite approach. In fact, disk galaxies are much easier to explain, while elliptical galaxies are more difficult.
Astronomers estimate that the galaxies formed when the huge gas clouds that existed in the early universe contracted. The huge gas cloud initially rotated very slowly. It gradually decreases in size and contracts due to its own gravity. The contraction of gravity shortens the radius of rotation of the gas cloud, and the gas cloud rotates faster to conserve angular momentum, collapsing into a flat disk. It’s easy to think of the process of quickly rolling out round dough to make flat pizza dough. This is the same reason why most planets in the solar system orbit in similar planes. To put it simply, a galaxy should be a giant version of our solar system. If galaxies were kneaded together by the contraction of giant clouds of gas, then all galaxies in the universe would have to be disk galaxies!
Astronomer Edwin Hubble, who first discovered that there is another galaxy outside our galaxy, also thought so at first. However, no matter how many times I looked, I observed too many round galaxies in the night sky. Hubble initially thought it was because he saw the flat-disk galaxy from various angles. When viewed from the side obliquely, it appears thin, but when viewed from the front it may appear round.
However, if only disk galaxies really exist in the universe, and galaxies appear round due to the angle at which they are observed, there should not be much difference in the number of galaxies that appear thin and galaxies that appear round. The degree of tilt of the observed galactic disk may be random. However, too many round galaxies were visible in the real universe. This clearly meant that there were galaxies in the universe that were actually round and ball-shaped, not flat disks. It was an elliptical galaxy.
The discovery of elliptical galaxies has left astronomers confused. As mentioned above, if galaxies are the result of a giant cloud of gas rotating and merging, it is natural that all galaxies have a disk shape. But why do non-flat, ball-shaped galaxies exist?
Astronomers have discovered an interesting fact. Elliptical galaxies were found in large numbers at the centers of galaxy clusters, where galaxies were crowded together at a greater density than in disk galaxies. This means that elliptical galaxies form more easily in regions of high galaxy density. Subsequently, as the dynamic movements of each star that makes up the galaxy were observed more closely, the secrets of the elliptical galaxies began to reveal themselves little by little.
The stars in a disk galaxy rotate in the same direction as the planets in the solar system. On the other hand, stars in elliptical galaxies rotate in complicated orbits. Elliptical galaxies can be seen as the result of collisions and mergers between relatively small disk galaxies. Because the random orbits of the stars that make up the galaxy are mixed in a complex way, the appearance can be seen as if the stars were round or scattered.
Up to this point it may seem that we have a fairly good understanding of the process of galaxy birth, but in reality this is not the case. All the stories so far are the most recent stories in the history of the universe and are just stories that correspond to modern and contemporary history in human history. Indeed, there are many secrets that have not yet been solved about how the first galaxies formed after the Big Bang and how the seeds of the first galaxies turned into the large galaxies of today. We still don’t know much about the ancient history of the universe.
In the mid-1990s, when the Hubble Space Telescope began observing the distant universe, astronomers began making interesting discoveries. For the first time we have finally confirmed the vague appearance of the first galaxies in the distant universe. Are the first galaxies really disk-shaped? Is it oval in shape? Funny enough, it was neither. It was a strange shape, round and long, like a pickle or a baguette.
Recent large-scale observations conducted by James Webb also reaffirm this point of view. In this study, astronomers captured about 50 very distant early galaxies through the CEERS observation project, which observes the early universe. We then conducted a 3D modeling analysis to estimate the actual shape of these galaxies. Taking views from various angles, we mathematically analyzed whether the galaxies were actually flat, elongated or rounded.
Interestingly, astronomers have broadly classified the shapes of primordial galaxies into four types based on their characteristics. ‘Volleyball’, which is round in all directions almost evenly like a ball, ‘Frisbee’, which is flat in one direction and round in the other direction, disc-shaped, ‘Surfboard’, which is flat in one direction and distorted into an oval shape in one direction and is round in two directions. “Pickle or noodle strings” long in one direction only.
In the relatively nearby universe, pickle-shaped galaxies make up about 25% of all galaxies. However, if we enter the early universe, 10 billion years ago, the percentage of pickle-shaped galaxies increases to 50-80%! It clearly shows that the first cosmic galaxies immediately after the Big Bang were not shaped like flat disks, round ovals or any other shapes familiar to us, but rather strange shapes like pickles.
How could these strange pickle-shaped galaxies exist in the early universe? The secret began to be revealed when it became possible to implement cosmological simulations using dark matter and dark energy via supercomputers.
In the universe that underwent inflation, or rapid expansion, soon after the Big Bang, density fluctuations occurred that reflected the quantum fluctuations that existed randomly in the beginning. Dark matter gathered around areas of higher density than the surrounding area, and dark matter was lost in all directions to areas of lower density. As a result, the framework of a gigantic cosmic structure was created in the universe, in which dark matter was entangled like a huge network. The long stream of dark matter is called a filament of cosmic macrostructure. Galaxies knead and form as matter flows along the filament.
At first the filament is not very thick because it has just been created. You can think of it as a thin straw. If you knead material flowing through a thin filament and create a galaxy inside it, you can create a galaxy shaped like an elongated cylinder like a pickle. Many recent cosmological simulations have recreated the pickle-shaped appearance of primordial galaxies born in the early universe in the distant past.
Brined primordial galaxies created in this way repeatedly collide and merge due to each other’s gravity. The first primordial galaxies contain abundant fresh gaseous material that will form young stars. When galaxies containing a lot of gaseous matter collide, a sort of frictional force can be created that kneads the material in the galaxy to form a flatter structure, similar to the viscosity of a fluid. In particular, because matter continues to flow in a constant direction along the filament structure, which has become much thicker than in the early universe, the growing galaxy has a component that rotates in the direction in which the material flowed. The birth of the rapidly rotating disk galaxies that exist in today’s universe is also reproduced naturally.
This is the big picture of the epic galactic evolution of our universe that astronomers are gradually completing today.
reference
https://ui.adsabs.harvard.edu/abs/2023arXiv231015232P/abstract
https://webbtelescope.org/contents/media/images/2024/104/01HHZE0D278BBH24A0YDY7ESQ3
Webb Shows Many Early Galaxies Looked Like Pool Noodles, Surfboards
What about writer Ji Woong-bae? I love cats and space. As a child, after watching “Galaxy Express 999”, I dreamed of promoting the beauty of the universe. He is currently researching evolution through the interaction of galaxies at the Galactic Evolution Research Center and Quasi-Cosmology Laboratory of Yonsei University, and is engaged in various scientific communication activities such as lectures and writings. He has written books such as “Astronomical Observatory”, “Thinking about the Universe All Day” and “The Science of Stars and Light”.
Ji Woong-bae, science columnist writer@bizhankook.com
[핫클릭]
·
[이주의 책] ‘Space Dust’ Ji Woong-bae guides you through space travel, “a piece of space every day”
·
[사이언스] Why hasn’t a planet twice the size of Earth been discovered?
·
[사이언스] How will humanity survive a solar explosion in 5 billion years?
·
[사이언스] “Small peppers are hot” Who ended the dark age of space?
·
[사이언스] Discovering the traces of the first generation of stars born in the universe
main article
Popular articles
#사이언스 #Discovering #Banana #Galaxy #universe
