Using the James Webb Space Telescope (JWST), researchers from the University of Copenhagen have achieved a groundbreaking feat: they have witnessed the formation of three of the earliest galaxies in the universe, occurring more than 13 billion years ago. This sensational discovery, published in the prestigious journal Science, provides invaluable insights into the early universe.

For the first time in the history of astronomy, researchers at the Niels Bohr Institute have observed the birth of three of the universe’s oldest galaxies, dating back to between 13.3 and 13.4 billion years ago. This discovery was made possible by the James Webb Space Telescope, which brought these unprecedented ‘live’ observations of galaxy formation to Earth.

Through the telescope, researchers observed large quantities of gas accumulating and coalescing into a nascent mini-galaxy. While this process has been hypothesized through theories and computer simulations, it had never been directly witnessed before.

These are the first ‘direct’ images of galaxy formation we’ve seen. While the James Webb has previously shown us early galaxies in later stages of evolution, we are now witnessing their very birth and the construction of the first stellar systems in the universe, said Assistant Professor Kasper Elm Heintz of the Niels Bohr Institute, who led the new study.

Galaxies Born Shortly After the Big Bang

The researchers estimate that the birth of these three galaxies occurred approximately 400 to 600 million years after the Big Bang, the explosion that initiated everything. Although this might seem like a long time, it corresponds to galaxies forming during the first three or four percent of the universe’s 13.8 billion-year lifespan.

Shortly after the Big Bang, the universe was an enormous opaque gas cloud composed of hydrogen atoms, unlike today’s night sky dotted with well-defined stars.

During the few hundred million years after the Big Bang, the first stars formed, before stars and gas began to combine into galaxies. This is the process we see beginning in our observations, explained Associate Professor Darach Watson.

The expansion of the Universe
The expansion of the Universe. Credit: NASA / Public domain / Wikimedia Commons

The birth of galaxies took place during a period in the universe’s history known as the Epoch of Reionization, when the energy and light from some of the earliest galaxies broke through the hydrogen gas haze.

It is precisely these large quantities of hydrogen gas that the researchers captured using the infrared vision of the James Webb Space Telescope. This is the most distant measurement of cold, neutral hydrogen gas, the building block of stars and galaxies, discovered by researchers to date.

The researchers were able to measure the formation of the universe’s first galaxies using sophisticated models of how light from these galaxies was absorbed by the neutral gas in and around them. This transition is known as the Lyman-alpha transition.

By measuring the light, the researchers could distinguish the gas from the newly formed galaxies from other gases. These measurements were only possible due to the incredibly sensitive capabilities of the James Webb Space Telescope’s infrared spectrograph.

Contributing to Understanding of Our Origins

The study was conducted by Kasper Elm Heintz, in close collaboration with colleagues Darach Watson, Gabriel Brammer, and Ph.D. student Simone Vejlgaard from the Cosmic Dawn Center at the Niels Bohr Institute, University of Copenhagen, a center dedicated to investigating and understanding the dawn of the universe. This latest result brings them much closer to achieving their goal.

The research team has already requested more observation time with the James Webb Space Telescope, hoping to expand on their new findings and learn more about the earliest epoch of galaxy formation.

For now, it’s about mapping our new observations of forming galaxies in greater detail than before. At the same time, we are constantly trying to push the boundary of how far we can see into the universe. So, maybe we’ll reach even further, said Simone Vejlgaard.

According to the researchers, this new knowledge helps answer one of humanity’s most fundamental questions.

One of the most fundamental questions humans have always asked is: ‘Where do we come from?’. Here, we piece together a bit more of the answer by shedding light on the moment when some of the universe’s earliest structures were created. It’s a process we will investigate further, until, hopefully, we can fit even more pieces of the puzzle together, concluded Associate Professor Gabriel Brammer.


University of Copenhagen | Kasper E. Heintz et al., Strong damped Lyman-α absorption in young star-forming galaxies at redshifts 9 to 11. Science 384, 890–894(2024). DOI:10.1126/science.adj0343

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