We have just seen the first galaxies in the universe being born

Scientists have just identified the formation processes of some of the Universe’s earliest galaxies in the turbulent epoch of the Cosmic Dawn.

JWST observations of the early Universe about 13.3 to 13.4 billion years ago, just a few hundred million years after the Big Bang, have revealed telltale signs of gas reservoirs actively sliding into three newly formed and growing galaxies.

“You could say that these are the first ‘live’ images of galaxy formation that we’ve ever seen,” says astrophysicist Kasper Elm Heintz of the Niels Bohr Institute in Denmark, who led the research.

“While James Webb [Space Telescope] has previously shown us the early galaxies in the later stages of evolution, here we witness their very birth, and thus, the construction of the first star systems in the Universe.”

Known as Cosmic Dawn, tthat first billion or so years after the Big Bang is shrouded in two things: mystery and the haze of neutral hydrogen that permeated the Universe and prevented light from spreading freely. The first, in fact, is a natural and direct consequence of the second, since light is the tool we use to understand the Universe.

JWST was designed, in part, as an attempt to penetrate this haze, since the infrared wavelengths at which it views the cosmos penetrate more easily and travel farther than other wavelengths. What we want to know is how it all came together, how, from a hot soup of primordial plasma, the first stars and galaxies coalesced, the fog cleared in the light of early objects, and the Universe took its baby steps toward that which is today.

So Heintz and his international team used JWST’s powerful infrared eye to look toward the Cosmic Dawn, where they detected a signal traced to three galaxies. Specifically, the signal emanated from the neutral hydrogen surrounding them as the gas absorbed and re-emitted the light of 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 all three galaxies some of the earliest discovered.

“These galaxies are like gaseous islands in a sea of ​​neutral, dark gas,” says Heintz.

Additionally, the researchers were able to distinguish gas reservoirs around galaxies from neutral intergalactic gas. These reservoirs were determined to be quite large, covering a fairly large portion of each galaxy, suggesting that they were actively forming galactic material. And the fact that there was so much of this gas also suggests that, at the time of the observations, the galaxies had not yet formed most of their stars.

“During the few hundred million years after the Big Bang, the first stars formed, before stars and gas began to coalesce into galaxies,” says cosmologist and astrophysicist Darach Watson of the Niels Bohr Institute. “This is the process we see the beginning of in our observations.”

We still have many questions about Cosmic Dawn. We have barely scratched the surface and many secrets still lie shrouded 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 galaxies are out there, we can look at them more closely to better understand the process of galaxy formation.

“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 bit more of the answer by shedding light on when some of the first structures of the Universe formed. It’s a process we’ll investigate further, until hopefully we’re able to fit even more pieces together. of the puzzle together.”

The research was published in science.