This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the early days of the universe, our home looked very different from how it does today. Back then, the region in our universe that would eventually become our Milky Way neighborhood was a collection of thousands of smaller galaxies—some pumping out tons of new stars, others filled only with gas or littered with dead stars and black holes.
You can watch how these galaxies coalesced over time and formed the familiar spiral disk we see today, thanks to a new set of simulations by a group of scientists led by Harley Katz, assistant professor of astronomy and astrophysics at the University of Chicago. The simulations, which took three years to run even on high-powered supercomputers, are the most detailed model to date of how a galaxy like the Milky Way might have evolved over the first several billion years of its existence. "What does the Milky Way look like at what we call cosmic dawn?" said Katz.
"For the first time, we can directly predict what the early Milky Way would have looked like to telescopes like Hubble or the James Webb Space Telescope." The six papers from the project, which is named MEGATRON, provide new insight into the makeup of early galaxies and how the elements formed over time. The papers are published in The Open Journal of Astrophysics. Since we cannot travel to the dawn of the universe to study it, one of the only ways we have to understand how space evolved over time is to build detailed computer models based on what we know about the laws of nature.
"Essentially, we put in all of the physics we think is relevant—gravity, hydrodynamics, radiation, chemistry, etc.—and then let it evolve and see if it reproduces what we actually see when we look around us today," said Katz. New data coming in from the powerful James Webb Space Telescope has added a new dimension to our understanding of the universe. So three years ago, a team of scientists undertook a project to incorporate this newfound knowledge into a model of what our galaxy might have looked like back in the first billion years of its existence.
Now they can compare it to the readings Webb gets today to see what matches and what's missing. If you run the clock back, the scientists said, you see a web of large and small galaxies of all different types, which will eventually merge into the modern Milky Way. "We follow thousands of subsystems in the model and directly compute what they all would have looked like with our most powerful space telescopes, which is many orders of magnitude more than what had been simulated before," said Katz.
"Within those you see an incredible diversity. Some of them are bursting out in star formation, others are dead, others are in the process of dying." One unique finding was that the model predicts the existence of "galaxies" that don't have any stars at all but still shine. Some of these might have once had stars that exploded or collapsed directly into black holes; others might have only ever contained gas.
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