Scientists have just identified it the formation processes of some of the universe’s earliest galaxies in the turbulent era of the Cosmic Dawn.
JWST observations of the early Universe some 13.3 to 13.4 billion years ago – just a few hundred million years after the Big Bang – have revealed telltale signs that reservoirs of gas are being actively slurped into three newly forming and growing galaxies.
“You could say these are the first ‘direct’ images of galaxy formation we have ever seen,” says astrophysicist Kasper Elm Heintz of the Niels Bohr Institute in Denmark, who led the study.
“While the James Webb [Space Telescope] has previously shown us early galaxies in later stages of evolution, here we are witnessing their birth, and thus the construction of the first galaxies in the universe.”
Known as the Cosmic Dawn, tThe first billion years after the Big Bang are shrouded in two things: mystery and the fog of neutral hydrogen that permeated the universe and prevented light from traveling freely. The former is in fact the natural and direct consequence of the latter, since light is the instrument we use to understand the universe.
JWST was designed in part as an attempt to penetrate this fog, because the infrared wavelengths in which it views the cosmos penetrate and travel further more easily than other wavelengths. What we want to know is how it all came together – how, from a hot primordial plasma soup, the first stars and galaxies came together, the fog cleared under the light of early objects, and how the universe took its small steps to what it is today. .
So Heintz and his international team used JWST’s powerful infrared eye to peer at the Cosmic Dawn, where they discovered a signal traced to three galaxies. Specifically, the signal emerged from the neutral hydrogen surrounding them, as the gas absorbed and re-emitted the light from the galaxies.
These galaxies, the researchers found, existed about 400 to 600 million years after the Big Bang, which occurred about 13.8 billion years ago. This makes the three galaxies among the earliest discovered galaxies.
“These galaxies are like sparkling islands in a sea of otherwise neutral, opaque gas,” says Heintz.
In addition, the researchers were able to distinguish the gas reservoirs around the galaxies from the intergalactic neutral gas. These reservoirs were found to be quite large and covered quite a large portion of each galaxy, indicating that they were actively forming into galactic material. And the fact that so much of this gas was present also suggests that the galaxies had yet to form most of their stars at the time of the observations.
“During the few hundred million years after the Big Bang, the first stars formed, before stars and gas began to combine into galaxies,” says cosmologist and astrophysicist Darach Watson of the Niels Bohr Institute. “This is the process we see the beginnings of in our observations.”
We still have many questions about the Cosmic Dawn. We have barely scratched the surface and there are still many secrets wrapped in neutral hydrogen, many of which have yet to be discovered. But the three galaxies discovered by Heintz and his team are a step forward. Now that we know the galaxies are there, we can take a closer look at them to better understand the galaxy formation process.
“One of the most fundamental questions we humans have always asked is: ‘Where do we come from?'” says astronomer Gabriel Brammer of the Niels Bohr Institute.
‘Here we piece together a little more of the answer by shedding light on the moment when some of the universe’s first structures were created. It’s a process we’ll explore further until we can hopefully fit even more pieces. of the puzzle together.”
The research was published in Science.