This illustration shows a galaxy forming just a few hundred million years after the Big Bang, when the gas was a mixture of transparent and opaque during the era of reionization. Data from NASA’s James Webb Space Telescope shows that there is a lot of cold, neutral gas in the vicinity of these early galaxies—and that the gas may be denser than expected.
Webb observed these galaxies as part of its Cosmic Evolution Early Release Survey (CEERS) a few months after it began making observations in 2022. CEERS includes both images and data known as spectra from the microgaps aboard its NIRSpec ( near infrared spectrograph). CEERS data were released immediately to support discoveries like this as part of Webb’s Early Release Science (ERS) program. Courtesy: NASA, ESA, CSA, Joseph Olmsted (STScI)
Using James Webb Space Telescoperesearchers from the University of Copenhagen became the first to see the formation of three of the earliest galaxies in the universe more than 13 billion years ago.
For the first time in the history of astronomy, researchers at the Niels Bohr Institute witnessed the birth of three of the absolute earliest galaxies in the universe, somewhere between 13.3 and 13.4 billion years ago.
The discovery was made using the James Webb Space Telescope, which brought these first “live observations” of forming galaxies to us here on Earth.
Through the telescope, the researchers were able to see signals from large amounts of gas accreting and accreting onto the forming mini-galaxy. Although this is how galaxies form according to theories and computer simulations, it has never been observed.
“These are arguably the first ‘direct’ images of galaxy formation we’ve ever seen. While James Webb previously showed us early galaxies at later stages of evolution, here we are witnessing their very birth and thus the building of the first star systems in the universe,” says Assistant Professor Kasper Elm Heinz of the Niels Bohr Institute, who leads the new study.
The research was published in the respected scientific journal Science.
How they did it
The researchers were able to measure the formation of the first galaxies in the universe by using sophisticated models of how the light from these galaxies is absorbed by the neutral gas found in and around them. This transition is known as the Lyman-alpha transition.
By measuring the light, the researchers were able to distinguish gas from newly formed galaxies from other gas. These measurements were only possible thanks to the incredibly sensitive capabilities of the infrared spectrograph on the James Webb Space Telescope.
Galaxies born shortly after the Big Bang
Researchers estimate that the birth of the three galaxies occurred approximately 400-600 million years after Big bang, the explosion that started it all. Although this sounds like a long time, it corresponds to galaxies forming in the first three to four percent of the universe’s total lifetime of 13.8 billion years.
Shortly after the Big Bang, the universe was a vast, opaque gas of hydrogen atoms—unlike today, where the night sky is dotted with a blanket of clearly defined stars.
“A few hundred million years after the Big Bang, the first stars formed before the stars and gas began to merge into galaxies. This is the process we see the beginnings of in our observations,” explains Associate Professor Darach Watson.
The birth of galaxies occurred at a time in the history of the universe known as the Age of Reionization, when the energy and light of some of the first galaxies broke through the haze of hydrogen gas.
It was these large amounts of hydrogen gas that were captured by the researchers using the infrared vision of the James Webb Space Telescope. This is the most distant measurement of the cold, neutral hydrogen gas that is the building block of stars and galaxies discovered by scientists to date.
For the early universe
The universe began its “life” about 13.8 billion years ago in a huge explosion – the Big Bang. The event produced an abundance of subatomic particles such as quarks and electrons. These particles aggregate to form protons and neutrons, which later fuse into atomic nuclei. Approximately 380,000 years after the Big Bang, electrons began orbiting atomic nuclei, and the universe’s simplest atoms gradually formed.
The first stars formed after several hundred million years. And in the hearts of these stars formed the larger and more complex atoms we have around us.
Later, the stars coalesce into galaxies. The oldest known galaxies formed about 3-400 million years after the Big Bang. Our own solar system originated about 4.6 billion years ago—more than 9 billion years after the Big Bang.
It contributes to the understanding of our origins
The study was conducted by Casper Elm Heinz in close collaboration with, among others, fellow researchers Darrah Watson, Gabriel Brammer and PhD student Simone Veilgaard of the Cosmic Dawn Center at the University of Copenhagen’s Niels Bohr Institute, a center whose stated aim is to explore and understand the dawn of the universe. This latest result brings them much closer to that.
The research team has already applied for more observing time with the James Webb Space Telescope, hoping to expand on their new result and learn more about the earliest era in galaxy formation.
“For now, it’s about mapping our new observations of galaxies forming in even greater detail than before.” At the same time, we are constantly trying to push the limit of how far into the universe we can see. So maybe we’ll go even further,” says Simon Veilgaard.
According to the researcher, the new knowledge contributes to an answer to one of the most basic questions of humanity.
“One of the most fundamental questions we humans have always asked ourselves is, ‘Where do we come from?’ Here, we piece together a little more of the answer by shedding light on when some of the universe’s first structures were created. This is a process that we will investigate further as we hope to be able to put together even more pieces of the puzzle,” concludes Associate Professor Gabriel Brammer.
Reference: “Strongly quenched Lyman-α absorption in young star-forming galaxies at redshifts 9 to 11” by Kasper E. Heinz, Darach Watson, Gabriel Brammer, Simon Weilgaard, Anne Hutter, Victoria B. Streit, Jorit Matti, Pascal A .Oesch, Páll Jakobsson, Nial R. Tanvir, Peter Laursen, Rohan P. Naidu, Charlotte A. Mason, Meghana Killi, Intae Jung, Tiger Yu-Yang Hsiao, Abdurro’uf, Dan Coe, Pablo Arrabal Haro, Steven L. Finkelstein and Sune Toft, 23 May 2024, Science.
DOI: 10.1126/science.adj0343
The study was conducted by researchers Kasper E. Heintz, Darach Watson, Gabriel Brammer, Simone Vejlgaard, Anne Hutter, Victoria B. Strait, Jorryt Matthee, Pascal A. Oesch, Pall Jakobsson, Nial R. Tanvir, Peter Laursen, Rohan P. Naidu , Charlotte A. Mason, Meghana Kiley, Intae Jung, Tiger Yu-Yang Hsiao, Abdurro’ouf, Dan Kou, Pablo Arabal Haro, Steven L. Finkelstein, and Sune Toft.
The Danish part of the study is funded by the Danish National Research Foundation and the Carlsberg Foundation.
