Just like humans, galaxies, such as the Milky Way, also tend to start chaotically, straightening themselves out into more recognizable shapes like spiral galaxies as they grow up and mature. Researchers tracked the development using a simulation in a supercomputer. 

Researchers from Lund University in Sweden used a supercomputer simulation that tracks the development of a galaxy over 13.8 billion years, the estimated age of our universe. They found that interstellar frontal collisions shape up chaotic young galaxies into spiral galaxies like the Milky Way.

The Milky Way, An Artist's Interpretation
(Photo: NASA/GSFC via Wikimedia Commons)

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Galaxies Maturing in the Universe

After the universe came into being right after the Big Bang event 13.8 billion years ago, it was widely believed to be a large, disordered mess. Galaxies collided with each other all the time, and stars formed at unusually high rates within massive gas clouds.

After a few billion years of this chaos across the universe, galaxies mature and start becoming more stable, taking on the form of the more organized spiral galaxies. However, a new growing body of research suggests that galaxies might have matured a lot faster than previously thought.

For example, a February 2021 study on the Science journal reports the discovery of a massive stellar bulge, a trait supposedly found in mature galaxies. It was found in a rotating galaxy just 1.2 billion years after the Big Bang. These galactic bulges refer to the tightly-packed group of stars, usually found in the bright centers of spiral galaxies.

Regardless of the rate at which it happened, the exact process remains largely unsolved to the scientific community. Researchers offer additional insight into this mystery in the article "VINTERGATAN - I. The Origins of Chemically, Kinematically, and Structurally Distinct Discs in a Simulated Milky Way- Mass Galaxy," appearing in the Monthly Notices of the Royal Astronomical Society.

Finding Hints, Traces from Milky Way

In their paper, the Lund University astronomers explain that spectroscopic surveys on the Milky Way have revealed a mix of spatial, chemical, and kinematic structures that give hints about its history.

Oscar Agertz, one of the authors of the study and an astronomy researcher at Lund University, explained in a university press release that they constructed a high-resolution simulation using a supercomputer that shows how young chaotic galaxies convert into well-ordered spirals and how they have evolved since the Big Bang. 

Researchers used the stars in the Milky Way as their reference since stars hold clues about distant epochs and even about the environment that created them. Using their positions, rates, and chemical compositions, the team used a supercomputer simulation to better understand the galaxy formation where these stars belong.

The Lund University team found out that if two large galaxies collide, a new disc could be formed around the older one, created by the large inflows of star-forming gases. The supercomputer simulation reveals that these discs, old and new, merged over billions of years, resulting in stable spiral galaxies with stars largely similar to those in the Milky Way.

Researchers hope that the new study could help future studies interpret existing and upcoming mappings of the Milky Way, pointing to a new direction that focuses on the interaction between galaxy collisions.


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