If you’ve ever been to a place with minimal light pollution and looked skywards at nighttime, you’ve probably seen our Milky Way galaxy. It manifests as a thick, hazy band of stars streaking across the sky.
“I like to think of the countless generations of our ancestors that looked up at the night sky and probably wondered, ‘Where did it come from? How old is it? Did it always look like this or did it look different in the past?’” said Andrew Wetzel, a professor in the Department of Physics and Astronomy at the College of Letters and Science at UC Davis.
Our ancestors across the globe had many names for the Milky Way. Winter Street, Silver River, Spirit Road, to name just a few. The Romans called it Via Lactea and said it was formed when Hercules was flung from the breast of his mother Hera, resulting in spilled milk.
“It turns out a lot of different cultures articulate kind of a similar flavor of origin story, where you have the flinging of milk, the sprinkling of water or the sprinkling of seeds, often in a rather chaotic manner, that then settled and led to the formation of our beautifully ordered Milky Way galaxy as we see it today,” Wetzel said.
Wetzel, who was presenting to a packed room at the February 2026 Astronomy on Tap event at Sudwerk Brewing Co., said that while our ancestors’ mythologies aren’t physically correct, the idea behind their stories is. Namely, the idea that out of chaos comes order.
How scientists study galaxy formation
Wetzel is a theoretical astrophysicist who ponders and models galaxy formation. Unlike the academics of yesteryear, the work isn’t all equations written in chalk on a blackboard. These days, it’s highly computational.
To put it simply, Wetzel translates the laws of physics into computer algorithms. He then uploads those algorithms to the world’s most powerful supercomputers, like the Pleiades supercomputer at NASA’s Ames Research Center, and generates computer simulations that model galaxy formation.
The theoretical research circumvents an observational problem. Specifically, our limited view of the universe.
“We have images, snapshots and times of these individual galaxies, but it’s not enough to understand how they evolve,” Wetzel said.
“Galaxies form and evolve across the full 13.8 billion years of history of the universe,” he added. “It can take a galaxy a billion years to change appreciably.”
And that’s where Wetzel’s theoretical work comes into play. His advanced supercomputer simulations, which can take on the order of a few million to 100 million CPU hours to run, are revealing the lifecycle of galaxies like our Milky Way.
How computer simulations reveal the Milky Way’s history
At the Astronomy on Tap event, Wetzel regaled the audience with a couple of his simulations. The cosmic movies trace the 13.8-billion-year history of a Milky Way-like galaxy’s formation. At first, the simulation shows tendrils of hydrogen gas coalescing in a gravitational dance.
“We sometimes say that galaxies form hierarchically. First little bits form and then gravity pulls them together to get bigger and bigger over time, but it’s quite chaotic,” Wetzel said. “Think about a bunch of cars entering an intersection from random directions all at the same time.”
Eventually, the hydrogen gas collapses and forms stars, which live out their lives and end in brilliant supernovae that push the hydrogen gas back out, becoming fodder for young stars. The process is a feedback loop.
“The early history of our Milky Way is marked by a lot of chaos,” Wetzel said. “However, as many billions of years go on, something remarkable happens. The Milky Way transitions from being chaotic to being ordered.”
This “order” is characterized by increasing inactivity, with the rate of star formation, supernovae and hydrogen gas feeding those processes all falling.
“This allowed the Milky Way to settle into a nice, stable, long-lived disk that we see today,” Wetzel said. “Out of chaos comes order.”
From chaos to order: the Milky Way’s evolution
The origin story of the Milky Way galaxy is deeply tied to the origin story of life on Earth. It’s thought that life on Earth arose roughly 4 billion years ago, right around the time that the Milky Way settled into its ordered, disk-like configuration, according to Wetzel.
“Think about it,” he said. “All that chaos, all those supernova explosions going off, it would have been difficult for life to emerge in such a chaotic setting.”
“But I also want to point out that there’s an interesting irony at play here,” he added. “Lots of supernova explosions probably inhibited the emergence of life, but ultimately, supernovae were vital to the emergence of life in our galaxy.”
The supernova explosions during the Milky Way’s early formation created the key elements necessary for life, such as carbon, oxygen and iron.
“It’s like sprinkling the seeds of life across the galaxy,” Wetzel said. “Sound a little familiar? Kind of like our ancestors’ origin stories, sprinkling seeds in a chaotic matter that eventually settled into our nice, working galaxy.”
What the Nancy Grace Roman Space Telescope will reveal about our galaxy
Wetzel closed his talk with a glimpse at the future of his field. Within the next two years, NASA plans to launch the Nancy Grace Roman Space Telescope. The instrument’s field of view will be 100 times greater than that of the Hubble Space Telescope.
“It’ll make Hubble seem like tunnel vision in comparison,” Wetzel said.
A wider field of view is important to understanding a cosmic structure as vast as the Milky Way. The Milky Way's billions of stars blend together across a huge swath of sky, making it difficult to discern them individually.
“The Nancy Grace Roman Space Telescope will produce a catalog of some 20 billion or more individual stars,” Wetzel said. “This will be the largest astronomical catalog ever created.”
While that 20 billion number only accounts for about one-fifth of the individual stars making up the Milky Way galaxy, it’s an exciting prospect for a theoretical and computational astrophysicist like Wetzel.
“We’re finally going to have the observational data we need that I can then calibrate or test against my simulations,” he said. “We’ll combine them to wind back the clock to really understand in exquisite detail for the first time, where did our galaxy come from? Just exactly, how did order come out of chaos?”
YOU MAY ALSO LIKE THESE STORIES
What Happens Inside a Black Hole? a UC Davis Astrophysicist Weighs In
How might falling into a black hole feel? Assuming you’re not ripped apart, a process called spaghettification, and your consciousness remains intact, UC Davis Assistant Professor of Physics and Astronomy Brenna Mockler has some ideas.
Simulations Explain Abundance of Bright Galaxies Observed at Cosmic Dawn
When researchers glimpsed the first images and data from the James Webb Space Telescope, humanity’s largest and most powerful space telescope, they noticed something peculiar. A large number of bright galaxies deep in the universe formed during a period called “Cosmic Dawn." New research published in The Astrophysical Journal Letters shows that a theoretical model produced roughly five years ago predicted these very observations and credits them to bursty star formation.