Scientists have just identified the formation processes of some of the oldest galaxies in the universe in the turbulent era of the Cosmic Dawn.
JWST observations of the early universe from about 13.3 to 13.4 billion years ago—just a few hundred million years after the Big Bang—revealed clear signs that reservoirs of gas were actively clustering into three newly forming and growing galaxies.
“This is arguably the first ‘direct’ image of galaxy formation that we have ever seen,” says astrophysicist Kasper Elm Heintz of the Niels Bohra 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 are witnessing their very birth and thus the construction of the first star systems in the universe.”
Known as Cosmic Dawn, i.eThe first billion years or so after the Big Bang are shrouded in two things: mystery and the nebula of neutral hydrogen that permeated the universe and prevented light from spreading freely. The former is actually a natural and direct consequence of the latter, since light is the tool we use to understand the universe.
JWST was designed in part as an attempt to penetrate this haze because the infrared wavelengths at which it observes space penetrate more easily and travel farther than other wavelengths. We want to know how it all came together—how the first stars and galaxies coalesced from the hot primordial plasma soup, the nebula spread out in the light of early objects, and the universe took its baby steps to what it is today. .
So Heintz and his international team used JWST’s powerful infrared eye to peer into the Cosmic Dawn, where they detected a signal traced across three galaxies. Specifically, the signal came from the neutral hydrogen that surrounded them as the gas absorbed and re-emitted the light of the galaxy.
Scientists found that these galaxies existed about 400 to 600 million years after the big bang, which took place about 13.8 billion years ago. This makes these three galaxies among the first to be detected.
“These galaxies are like sparkly islands in a sea of ​​otherwise neutral, opaque gas,” Heintz says.
In addition, scientists were able to distinguish gas reservoirs around galaxies from intergalactic neutral gas. These basins were determined to be quite large and cover quite a large portion of each galaxy, suggesting that they were actively forming into galactic material. And the fact that there was so much of this gas also suggests that the galaxies had not yet formed most of their stars at the time of observation.
“Within a 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 a process that we see the beginning of in our observations.”
We still have a lot of questions about Cosmic Dawn. We have barely scratched the surface, and there are still many mysteries wrapped up 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 process of galaxy formation.
“One of the most fundamental questions we humans always ask ourselves is, ‘Where did we come from?'” says astronomer Gabriel Brammer of the Niels Bohra Institute.
“Here, we’re piecing together a little more of the answer by shedding light on when some of the earliest structures of the universe were formed. It’s a process we’ll continue to investigate until, hopefully, we’re able to fit even more pieces.” puzzle together.”
The research was published in Science.