Astronomers have used the
James Webb Space Telescope (
JWST) to observe some of the oldest galaxies in the Universe, in the midst of their formation. This discovery brings us closer to understanding the beginnings of our cosmos.
Illustration of a galaxy forming a few hundred million years after the Big Bang, during a time when the gas was a transparent/opaque mixture during the reionization era.
Credit: NASA, ESA, CSA, Joseph Olmsted (STScI)
A research team published a study in
Science on May 23 revealing the detection of three forming galaxies, dating from 400 to 600 million years after the Big Bang. These galaxies are emerging from a primordial cloud of hydrogen and helium, an observation made possible by the capabilities of the JWST.
This discovery allows us to explore the era of reionization, a crucial period when the first stars and galaxies began to light up the Universe by dissipating the surrounding dark clouds of gas. The JWST observed 12 galaxies from this era, when the Universe was only 3% of its current age.
By analyzing the light spectra of these galaxies, researchers detected signs of absorption by large amounts of neutral hydrogen. This indicates that these galaxies were in the process of transforming this gas into new stars.
This stage of stellar formation played a key role in bringing the Universe out of the "cosmic dark ages" and into the era of reionization. The new stars and galaxies ionized the surrounding gas, making the Universe increasingly transparent.
The JWST had previously identified galaxies from this era, but this is the first time it has observed their formation. This allows us to understand how the first stellar systems formed and evolved.
These observations are crucial for answering essential questions about the nature of the first gas clouds and the process by which galaxies emerged. If these discoveries are confirmed by further studies, they could illuminate many aspects of the Universe's evolution.