To test these emerging theories, researchers are using advanced computer simulations to study the infant universe. “There’s actually been really remarkable progress since Webb launched, really in the last year or so, on numerical simulations,” Somerville told attendees. She added that the latest models “perhaps are more appropriate and more informative for interpreting observations in the high-redshift universe.”
As these simulations become more sophisticated, the James Webb Space Telescope (JWST) is identifying an increasing number of distant galaxies. By comparing JWST observations of the early universe with simulations designed to explain them, scientists are moving closer to understanding the true origins of cosmic dawn.
“We can try to match the best analogue of the observed galaxy to the simulated [galaxy],” said Hakim Atek, an astrophysicist at 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 important clue has recently emerged from JWST’s Mid-Infrared Instrument (MIRI), a supercooled instrument capable of separating and analyzing light from extremely distant objects. MIRI observations suggest that early galaxies did not all share the same characteristics, contrary to what some scientists had expected.
“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 unexpected diversity could indicate that star formation in the early universe occurred in powerful bursts. Galaxies may have cycled through periods of intense stellar birth, followed by explosions that expelled gas and temporarily halted star formation. Over time, the gas could have gathered again, triggering new generations of stars.
“Some of them, it looks like they cleared all the interstellar medium that is present there, the gas and the dust. It’s like you’re looking only at naked stars,” Atek said. “Another galaxy is the opposite. It has a lot of gas.”
Another clue comes from a group of early galaxies containing unusually high levels of nitrogen. This chemical signature may point to the presence of extremely massive stars in the young universe. Simulations indicate that these massive stars could produce excess nitrogen before exploding as supernovas and distributing the element throughout their host galaxies.
Researchers may eventually piece together the complete story of how the first galaxies formed and evolved. For now, they continue to study the evidence found in JWST observations and increasingly detailed simulations of the early universe.
The Puzzle of Existence
When the first stars and galaxies began shining, the universe underwent a dramatic transformation. Radiation from these early galaxies and black holes ionized vast regions of neutral hydrogen gas, carving enormous bubbles through the cosmic haze. Scientists call this era reionization because it marked the universe’s second major phase of ionization. It also brought the cosmic dark age to an end—a period when the universe was largely obscured and devoid of stars.
The first stars may have been hundreds or even thousands of times more massive than the Sun. They rapidly consumed their hydrogen and helium fuel before ending their lives in powerful supernova explosions. These events scattered newly forged elements—including carbon, nitrogen, oxygen, phosphorus, and iron—throughout space, creating the raw materials needed for planets and life.
Source: www.wired.com