Using the James Webb Space Telescope, scientists have discovered that early universe galaxies must have grown up way faster than expected. Plus, the same team also found that, 10 billion years ago, the cosmos wasn’t quite as disordered and chaotic as previously believed.
The international team, led by researchers from Durham University in the U.K., reached these conclusions by discovering evidence of structures called “star bars” forming in galaxies that existed just a few billion years after the Big Bang.
Star bars are elongated regions of increased star density found at the hearts of spiral galaxies like the Milky Way and other disk galaxies. As they form, star bars push gas toward the hearts of their respective galaxies, thereby regulating star birth. The presence of these central bar structures thus indicate that a galaxy has entered a more settled and “mature phase.”
“Galaxies in the early universe are maturing much faster than we thought,” Zoe Le Conte, team leader and a researcher at Durham University, said in a statement. “This is a real surprise because you would expect the universe at that stage to be very turbulent, with lots of collisions between galaxies and a lot of gas that hasn’t yet transformed into stars.
“However, thanks to the JWST, we are seeing a lot of these bars much earlier in the life of the universe, which means that galaxies were at a more settled stage in their evolution than previously thought. This means we will have to adjust our views on early galaxy evolution.”
Bar-hopping for the James Webb Space Telescope
This isn’t the first time scientists have gone bar-hopping in the early history of the 13.8 billion-year history of the universe.
The Hubble space telescope witnessed these features as well, but that orbiting eye on the universe could only go as far back as 8 billion to 9 billion years. The increased sensitivity and wavelength range of the JWST, however, has stretched such observations back at least another 1 billion years. This has revealed bar formation in galaxies that are seen as they were between 8 billion and 11.5 billion years ago. In fact, of 368 disk galaxies the team considered for the study, 20% already had bars.
That is double the number observed by Hubble.
“We find that many more bars were present in the early universe than previously found in Hubble studies, implying that bar-driven galaxy evolution has been happening for much longer than previously thought,” team member and Durham University scientist Dimitri Gadotti said. “The fact that there are a lot more bars is what’s very exciting.”
The further back in time the team looked with the JWST, the fewer bar structures they observed in galaxies.
They believe this could be because galaxies at earlier stages of the universe were not as well formed. An alternative may be that shorter bars were more common in progressively earlier galaxies. Even the impressive observational power of the JWST isn’t sufficient to see these short bars in early galaxies.
With these results in hand, the team now wants to use the JWST to peer even further back into cosmic time, looking back as far as 12.2 billion years ago. This could reveal whether bar growth was common just 1.6 billion years after the Big Bang.
“The simulations of the universe now need to be scrutinized to see if we get the same results as the observations we’ve made with the JWST,” Gadotti concluded. “We have to think outside of what we thought we knew.”
The team’s research was published in the journal Monthly Notices of the Royal Astronomical Society.
