James Webb Space Telescope sees early galaxies defying ‘cosmic rule’ of star formation

The James Webb Space Telescope (JWST) discovered that galaxies in the early universe were cosmic rule breakers. This discovery sheds light on how early galaxies evolved and the fundamental processes that shaped them the universe as we see it today.

To find out the truth about these cosmic mockeries, a team of astronomers used JWST look back over 12 billion years time and trace the galaxies and the rules they followed throughout cosmic history. The team found that the same rules that connected the rate of star birth to galactic masses and chemical compositions held constant. But these rules only go so far. The earliest galaxies defied them.

It was as if galaxies had a set of rules they followed – but amazingly, this cosmic set of rules appears to have been dramatically rewritten in the universe’s infancy,” said Claudia Lagos, associate professor at the University of Western Australia. said in a statement. “The most surprising discovery was that ancient galaxies produced far fewer heavy elements than we would have predicted based on what we know about galaxies that formed later.”

This difference had not been noticed before because the instruments used before JWST were not powerful enough to see the chemical composition of galaxies as early as about 11 billion years ago. However, JWST allowed this team to look back just a few hundred million years after the Big Bang, revealing a break in the relationship between star formation, mass and chemistry.

Related: The James Webb Space Telescope detected the first evidence of carbon on Jupiter’s icy moon Europa

When did things get tough for space?

When the universe first began to form stars and in galaxies it was filled with hydrogen and helium—the two lightest elements—with the former being by far the more dominant.

Only a few heavier elements—what astronomers call metals—existed until the first generation of stars forged them in their hearts and then dispersed them through the universe by massive means at the end of their lives. supernova explosions.

This material was eventually incorporated into the next generation of stars, meaning that these stars, and therefore the galaxies in which they sit, had a higher concentration of metals – a measure called “metallicity”. This process of metal enrichment has continued throughout 13.8 billion years of cosmic history, meaning that early galaxies are expected to have lower metallicities than their modern counterparts.

But even taking this into account, the team found that the metallicity of the early galaxies was still lower than expected. Much lower.

“Their chemical abundances were roughly four times lower than expected based on the fundamental metallicity seen in later galaxies,” Lagos continued, explaining that the early galaxies the team observed held even more surprises.

The team hypothesizes that the difference may exist because galaxies that are only a few hundred million years after the Big Bang may still be tightly bound by the intergalactic medium—the hot gas and dust that exists between galaxies.

“Early galaxies continuously received new primordial gas from their surroundings, with the influx of gas diluting the heavy elements inside the galaxies, making them less concentrated,” Lagos concluded.

As such, the team’s findings may challenge current models of galaxy evolution and the mechanism that facilitated the development of the first galaxies.

The study was published on September 21 journal Nature.