Scientists from the University of Portsmouth have discovered that water was already present in the Universe 100-200 million years after the Big Bang.
The discovery means habitable planets could have started forming much earlier - before the first galaxies formed and billions of years earlier than was previously thought.
The study was led by astrophysicist Dr Daniel Whalen from the University of Portsmouth's Institute of Cosmology and Gravitation . It is published today (3 March 2025) in Nature Astronomy .
It is the first time water has been modelled in the primordial universe.
According to the researchers' simulations, water molecules began forming shortly after the first supernova explosions, known as Population III (Pop III) supernovae. These cosmic events, which occurred in the first generation of stars, were essential for creating the heavy elements - such as oxygen - required for water to exist.
The key finding is that primordial supernovae formed water in the Universe that predated the first galaxies.
Dr Daniel Whalen , from the University of Portsmouth's Institute of Cosmology and Gravitation
Dr Whalen said: "Before the first stars exploded, there was no water in the Universe because there was no oxygen. Only very simple nuclei survived the Big Bang - hydrogen, helium, lithium and trace amounts of barium and boron.
"Oxygen, forged in the hearts of these supernovae, combined with hydrogen to form water, paving the way for the creation of the essential elements needed for life."
The researchers examined two types of supernovae: core-collapse supernovae, which produce a modest amount of heavy elements, and the much more energetic Pop III supernovae, which eject tens of solar masses of metals into space. Both types of supernovae, the study found, formed dense clumps of gas enriched with water.
While the overall amount of water produced in these early supernovae was modest, it was highly concentrated in dense regions of gas, known as cloud cores, which are thought to be the birthplaces of stars and planets. These early water-rich regions likely seeded the formation of planets at cosmic dawn, long before the first galaxies took shape.
Dr Whalen said: "The key finding is that primordial supernovae formed water in the Universe that predated the first galaxies. So water was already a key constituent of the first galaxies.
"This implies the conditions necessary for the formation of life were in place way earlier than we ever imagined - it's a significant step forward in our understanding of the early Universe.
"Although the total water masses were modest, they were highly concentrated in the only structures capable of forming stars and planets. And that suggests that planetary discs rich in water could form at cosmic dawn, before even the first galaxies."
The research is a collaboration between the University of Portsmouth in England and the United Arab Emirates University.
