Evrim Yazgin
Cosmos science journalist
The James Webb Space Telescope has allowed astronomers to see, for the first time, the birth of the earliest galaxies in the universe between 13.3 and 13.4 billion years ago.
These galaxies formed when the universe was only about 400–600 million years old – when the universe was roughly 3 to 4% of its current age. The discovery will help build a picture of the history and evolution of the universe.
Researchers at the Niels Bohr Institute at the University of Copenhagen in Denmark used JWST data to witness the birth of 3 of the first galaxies in the cosmos. Their findings are published in the journal Science.
“You could say that these are the first ‘direct’ images of galaxy formation that we’ve ever seen,” says first author Kasper Elm Heintz. “Whereas the James Webb has previously shown us early galaxies at later stages of evolution, here we witness their very birth, and thus, the construction of the first star systems in the universe.”
“During the few hundred million years after the Big Bang, the first stars formed, before stars and gas began to coalesce into galaxies,” explains co-author Darach Watson. “This is the process that we see the beginning of in our observations.”
Using JWST, the astronomers observed huge volumes of gas accumulating onto a ‘mini galaxy.’
While theories and computer simulations have suggested this is how galaxies are formed, it has never been seen before now.
JWST’s infrared instruments spotted large amounts of hydrogen gas in the ancient universe. It is the most distant measurement of cold, neutral hydrogen gas – the building block of stars and galaxies.
“For now, this is about mapping our new observations of galaxies being formed in even greater detail than before,” says co-author and PhD student Simone Vejlgaard. “At the same time, we are constantly trying to push the limit of how far out into the universe we can see. So, perhaps we’ll reach even further.”
“One of the most fundamental questions that we 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 that some of the universe’s first structures were created,” adds co-author Gabriel Brammer.
