June 23, 2024


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We've just seen the birth of the first galaxies in the universe: ScienceAlert

We've just seen the birth of the first galaxies in the universe: ScienceAlert

Scientists have just determined Formation processes of some of the universe's first galaxies 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 – have revealed clear signs of gas reservoirs actively flowing into three newly forming and growing galaxies.

“These are arguably the first ‘direct’ images of galaxy formation that we have ever seen.” says astrophysicist Kasper Elm Heintz from the Niels Bohr Institute in Denmark, who led the research.

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

Known as the Cosmic Dawn, RThe first billion years or so after the Big Bang were shrouded in two things: mystery, and a fog of neutral hydrogen that permeated the universe and prevented light from spreading freely. The former is, in fact, the natural and direct consequence of the latter, because light is the tool we use to understand the universe.

The James Webb Space Telescope was designed, in part, as an attempt to penetrate this fog, since the infrared wavelengths through which the universe is seen penetrate more easily. Travel further Of 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 in the light of the early objectsThe universe took its baby steps towards where it is today.

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So, Heintz and his international team used JWST's powerful infrared eye to look toward the cosmic dawn, where they detected a signal dating back to three galaxies. Specifically, the signal was emitted by the surrounding neutral hydrogen as it absorbed the gas and re-radiated the galaxies' light.

The researchers found that these galaxies 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 first to be discovered.

An artistic visualization of the formation of galaxies at the beginning of the universe. (NASA, ESA, Canadian Space Agency, Joseph Olmstead/STScI)

“These galaxies are like sparkling islands in a sea of ​​opaque, neutral gases.” Heintz says.

Furthermore, the researchers were able to distinguish perigalactic gas reservoirs from neutral intergalactic gas. These reservoirs were determined to be very large, covering a very large proportion of each galaxy, indicating that they were actively forming in galactic matter. The fact that there is so much of this gas also indicates that at the time of observation, the galaxies had not yet formed most of their stars.

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

We still have a lot of questions about the cosmic dawn. We've barely scratched the surface, and there are still many secrets 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 that galaxies exist, we can look at them more closely to better understand the process of galaxy formation.

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“One of the basic questions we humans always ask is: Where do we come from?” says astronomer Gabriel Brammer From the Niels Bohr Institute.

“Here, we piece together more answers by shedding light on the moment when some of the universe's first structures were created. It's a process we will investigate further, so that we can hopefully fit more pieces of the puzzle together.”

The research was published in Sciences.