Water may have first formed 100–200 million years after the Big Bang, according to a modeling paper published in Nature Astronomy. The authors suggest that the formation of water may have occurred in the universe earlier than previously thought and may have been a key constituent of the first galaxies.
Water is crucial for life as we know it, and its components—hydrogen and oxygen—are known to have formed in different ways. Lighter chemical elements such as hydrogen, helium and lithium were forged in the Big Bang, but heavier elements, such as oxygen, are the result of nuclear reactions within stars or supernova explosions. As such, it is unclear when water began to form in the universe.
Researcher Daniel Whalen and colleagues utilized computer models of two supernovae—the first for a star 13 times the mass of the sun and the second for a star 200 times the mass of the sun—to analyze the products of these explosions. They found that 0.051 and 55 solar masses (where one solar mass is the mass of our sun) of oxygen were created in the first and second simulation, respectively, due to the very high temperatures and densities reached.
Whalen and colleagues found that as this gaseous oxygen cooled and mixed with the surrounding hydrogen left behind by the supernovae, water formed in the leftover dense clumps of material. These clumps were likely to be sites for the formation of the second generation of stars and planets.
In the first simulation, the authors found that the mass of water reached quantities that were about the equivalent of one hundred millionth to one millionth of a solar mass in 30 to 90 million years following the supernova. In the second simulation, the amount of water reached roughly 0.001 solar masses after 3 million years.
The authors suggest that if water could survive the formation of the first galaxies, a potentially destructive process, it could have been incorporated into the formation of planets billions of years ago.
More information:
D. J. Whalen et al, Abundant water from primordial supernovae at cosmic dawn, Nature Astronomy (2025). DOI: 10.1038/s41550-025-02479-w
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Water might be older than we first thought, forming a key constituent of the first galaxies (2025, March 3)
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