Recent research led by a team at Portsmouth University and the United Arab Emirates University suggests that water began appearing in large quantities long before our Sun was born—possibly within just 100–200 million years after the Big Bang.
In the new study, the team conducted a series of computer simulations which found that the first supernova explosions produced surprising amounts of water, hinting that one of life’s key ingredients appeared in the universe far earlier than once thought.
Did the early Universe make water with a bang?
Not long after the Big Bang, the universe was dark, mostly filled with hydrogen and helium gas. As the first stars—Population III or “Pop III” stars—began to shine, they introduced light into this darkness and paved the way for all later generations of stars and galaxies. Pop III stars were enormous compared to most stars we see today with a mass equivalent to around 200 Suns, and they helped create the heavier elements necessary for life, including oxygen.
Because these initial stars contained almost no heavy elements, many scientists assumed that the early universe was too “barren” for water to form in significant amounts. As most middle school students can tell you, water requires both hydrogen (abundant everywhere from the Big Bang) and oxygen. When large stars die in spectacular supernova blasts, they scatter oxygen and other heavy elements into their surroundings.
Using modern simulations, the researchers tracked how this oxygen mixed with the surrounding hydrogen to form water in the chaotic aftermath of these first stellar explosions.
The simulations focused on two different types of early supernovae. One involved a relatively modest 13-solar-mass star that lived about 12 million years before exploding, while the other was a titanic 200-solar-mass star that lived only 2.6 million years. In the cosmic timeline—where the universe is 13.8 billion years old—these events took place when the universe itself was a relative toddler. Despite the difference in their energies and explosion sizes, each supernova ejected large amounts of oxygen into the surrounding gas.
After each supernova, hot gas bubbles expanded, then cooled and condensed into various structures. Key reactions between oxygen and hydrogen began to take place, leading to the creation of water molecules. In low-density regions, water formed but only in small amounts, since those areas did not foster many collisions between molecules. However, water accumulated in much higher concentrations in denser clumps of gas—so-called “cloud cores” that were enriched by metals from the explosions. As these clumps continued to collapse under their own gravity, the water production rate skyrocketed, ensuring that, by the end of the simulations, some dense cores had water abundances not far below those in our solar system today.
The paper says that these dense, dust-filled cores could easily evolve into the types of disks around young stars where Jupiter-mass planets could have taken shape. This means that in the very early universe, there may have been potential “planet nurseries” already containing plentiful water.
Although the universe was harsh at these times, with intense ultraviolet radiation from newly formed stars, these simulations demonstrate that dust grains and dense gas can act as a shield to protect water molecules from being destroyed. Over time, as more stars and galaxies began to form, the water carried into these young galaxies could have laid the foundations for more complex chemistry and, eventually, for life itself.
In theory, if astronomers look at sufficiently early periods of cosmic history, certain emission lines from heated water vapor could be picked up by instruments like the Atacama Large Millimeter/submillimeter Array (ALMA). Closer to home, any planets forming around the earliest metal-poor stars might contain traces of this primeval water, offering insight into how common life-friendly conditions might be on a galactic scale.
While the researchers say it’s still a big leap to say that life could have arisen there, these findings at least show that one of life’s essential ingredients—liquid water—was in no short supply.
The findings appeared in the preprint server arXiv.
