GoKawiilThe galaxy on the screen represented an early population, but the most ancient galaxy discovered by JWST so far existed only 280 million years after the Big Bang. The telescope’s bewildering discovery of bright, early galaxies initially led some scientists to suggest that our understanding of fundamental cosmology, the laws that govern the behavior of energy and matter in the early universe, may be flawed. But after a few years of studying these primitive objects, theorists now have several models to explain their brightness and abundance.
“We almost have gone from having too many early galaxies to having too many theories to explain them,” Somerville told the room.
Perhaps the first galaxies converted gas to stars more efficiently than previously thought. Or they experienced periodic bursts of star formation driven by turbulent conditions. Or maybe early star-forming regions preferentially created massive, extremely bright stars. Many astrophysicists think some combination of these factors, and perhaps others, contributed to the galaxies’ development.
We almost have gone from having too many early galaxies to having too many theories to explain them. Rachel Somerville, Flatiron Institute
To test these new ideas, researchers are exploring the infant universe through simulations. “There’s actually been really remarkable progress since Webb launched, really in the last year or so, on numerical simulations,” Somerville told attendees, adding that these new simulations “perhaps are more appropriate and more informative for interpreting observations in the high-redshift universe.”
As these models improve, JWST is documenting more and more galaxies. By comparing what it sees in the early universe to simulations that attempt to explain why, researchers are inching closer to uncovering the true nature of cosmic dawn.
“We can try to match the best analogue of the observed galaxy to the simulated,” said Hakim Atek, an astrophysicist with the Paris Institute of Astrophysics at Sorbonne University. “Once you have this best match, you can look at the star formation history, because in the simulations you have access to the whole history of the galaxy.”
An intriguing clue has recently emerged from JWST’s Mid-Infrared Instrument (MIRI), a supercooled device that can split apart the light of distant objects. MIRI has revealed that early galaxies do not have the same traits, as scientists assumed.
“The main surprise is the diversity of the properties of galaxies we are seeing at early epochs,” Atek said. “You’re expecting that they would look the same.”
This diversity may be an indication of star formation that occurred in bursts, as galaxies cycled through periods of fusing stars that exploded and expelled gas clouds, halting the creation of stars, only for the gas to gather again and trigger a new wave of stellar birth.
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