The James Webb Space Telescope (JWST) continues to set milestones in astronomical research. Recently, scientists at the University of Copenhagen, Denmark, used the ultrasensitive instrument to observe, for the first time in history, the formation of three of the first galaxies to appear in the universe.
According to the most accepted cosmological model, the universe is about 13.8 billion years old. Scientists at the Niels Bohr Institute collected direct information from galactic births dating back 13.3 to 13.4 billion years ago. The galaxies found formed, on average, 400 million years after the Big Bang, when the universe was 4% of its current age.
It should be remembered that since light has a finite speed of 300,000 m/s, and since space is expanding, observing light from very distant objects is equivalent to seeing what they were like a long time ago. If a sufficiently distant observer pointed a telescope at Earth, he could see, for example, the Jurassic period in full swing. Likewise, JWST, by having the ability to observe deeply into the distant universe, therefore has the ability to observe some aspects of the early universe.
The recent observations of the James Webb have not resulted in exactly photographs like the ones it has accustomed us to during its two years of operations. The Copenhagen scientists clarify that they saw signs of large amounts of gas accumulating around a mini galaxy in the process of construction. The JWST data are the most distant measurements of cold, neutral hydrogen gas recorded to date. This is the theoretical mechanism and the original raw material by which galaxies and stars were born.
“You could say that these are the first direct images of galaxy formation that we have seen. While the James Webb had previously shown us early galaxies in later stages of evolution, here we witness their birth and therefore the construction of the first star systems in the universe,” explained Associate Professor Kasper Elm Heintz of the Institute. Niels Bohr, who led the study.
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The primitive and dark universe
After the Big Bang universal expansion event, it took hundreds of millions of years for the universe to start making stars. The Niels Bohr Institute describes those first moments of the cosmos as an opaque cluster of hydrogen atoms where there were no stellar bodies, only gas. Eventually, that stellar matter collapsed in on itself, leading to the birth of the first stars. Antlers, in turn, grouped together to form the first galaxies.
For some time, even though the stars were already forming, the primitive conditions of the universe prevented their light from being dispersed. Just as, on a foggy morning, the haze obscures the light from streetlights, the light from galaxies was lost in the surrounding hydrogen clouds. It is thanks to the radiation of the first celestial bodies that the surrounding gas was ionized and became “transparent” for photons, the elementary particles that make up light. This early period of the universe is known as “the reionization stage.” When it ended 900 million years later, the universe was observable.
As the use of the James Webb Space Telescope is refined, scientists are getting closer to the earliest moments of the Universe.
The Copenhagen team has published their results in an article in Science where they detail the current limits of the JWST infrared sensors. They hope to surpass their own record to continue exploring the clouds of neutral hydrogen gas that enveloped galaxies while dimming their brightness in the early universe.
