For the first time in the history of astronomy, scientists at the Niels Bohr Institute have witnessed the birth of three of the oldest galaxies in the universe, between 13.3 and 13.4 billion years ago.
The discovery, published in Science, was made using the James Webb Space Telescope, which obtained these first “live observations” of galaxies forming in the most distant universe.
Through the telescope, researchers were able to see signs of large amounts of gas accumulating and accreting into a mini galaxy in the process of construction. While this is how galaxies form according to theories and computer simulations, it has never actually been witnessed.
“You could say that these are the first ‘direct’ images of galaxy formation that we have seen. While Webb had previously shown us early galaxies in later stages of evolution, here we witness their birth and therefore their the formation of the first star systems in the universe,” Associate Professor Kasper Elm Heintz of the Niels Bohr Institute, who led the new study, said in a statement.
Researchers estimate that the birth of the three galaxies occurred approximately 400 to 600 million years after the Big Bang, the explosion that started it all. While that seems like a long time, it corresponds to galaxies forming during the first 3-4% of the universe’s total lifespan of 13.8 billion years.
Shortly after the Big Bang, the universe was a huge opaque gas of hydrogen atoms, unlike today, where the night sky is dotted with a blanket of well-defined stars.
“During the few hundred million years after the Big Bang, the first stars formed, before stars and gas began to merge into galaxies. This is the process that we see the beginning of in our observations,” explains the Associate Professor Darach Watson.
The birth of galaxies took place at a time in the history of the universe known as the Epoch of Reionization, when the energy and light of some of the first galaxies passed through fogs of hydrogen gas.
It is precisely these large amounts of hydrogen gas that researchers captured using the infrared vision of the James Webb Space Telescope. This is the most distant measurement of the cold, neutral hydrogen gas, which is the building block of stars and galaxies, discovered to date by scientific researchers.
