Like cosmic toddlers, galaxies in the young universe were messy and struggled to settle down, a new study finds.
Use the powerful James Webb Space Telescope (JWST), scientists have observed more than 250 galaxies in the early universe. The research team mapped the movement of gas a long time ago, when the universe was growing, between 800 million and 1.5 billion years after the Big Bang. (The cosmos is roughly 13.8 billion years.)
“Most of the galactic population is going through a turbulent phase in its evolutionary history,” lead author Lola Danhaivedoctoral student at the Kavli Institute of Cosmology at the University of Cambridge, told Live Science in an email.
Unlike previous studies, Danhaive explained, the team targeted less massive galaxies and discovered what they called “disordered kinematics,” meaning that the galaxies the researchers studied were not stable, rotating disks like the Milky Way and its neighbors.
Turbulence during the early phases of the universe’s history was much higher than scientists previously thought, Danhaive added, because previous studies were oriented toward larger, more ordered galaxies, which are easier to spot in telescopes than the smaller galaxies targeted in the new study.
“We find evidence that this turbulence in the (galaxy) disk is caused by large amounts of gas, which fuels intense star formation and leads to gravitational instabilities,” Danhaive said.
Additionally, the researchers observed how galaxies evolved from these chaotic structures to the more regular patterns seen in mature galaxies, providing unprecedented insight into how galaxies grew from youth to maturity.
“At first, galaxies go through a turbulent assembly phase, during which strong bursts of star formation and large amounts of gas disrupt the orderly movements of the gas disk,” Danhaive said. “Later, galaxies increase their mass and become more stable.”
Structures like the Milky Way formed more recently, over the past billion years, as available gas was absorbed by stars and diminished throughout the galaxy. Less free-floating gas allows mature galaxies to grow and change more easily than in their youth.
The study would not have been possible without the JWST, which is perched in a remote, gravitationally stable location in space, far from stray light from the Earth and Moon. The infrared telescope can peer deeper into space than any of its predecessors and regularly discovers galaxies considered to be the oldest in the known universe. Danhaive said the observatory, combined with simulations, helps researchers better understand “burst” star formation and how gas influences a galaxy’s disk.
“Overall, our work provides a window into the dynamics of early galaxy formation,” she said. Next, the team plans to study gas inflows and outflows in individual galaxies by tracing how the gas became chemically enriched.
Researchers expect the incoming gas to be less enriched, or “Perfect“, while the outgoing gas will contain more chemical components, thanks to contributions from the galaxy’s individual stars. Examining how gas flows through the galaxy could allow researchers to understand why some galaxies spin faster than others, for example.
“There is so much more to discover thanks to the incredible capabilities of JWST, and we look forward to exploring many more aspects of early galaxy formation,” Danhaive said.
