Conventional scientific theory holds that water — composed of two hydrogen atoms coupled to a single oxygen atom — was something of a Johnny-come-lately to the Universe as we know it today. Oxygen is heavier than helium, helium being formed as a result of nuclear fusion of hydrogen as stars burn up their fuel. Other, heavier elements, like oxygen, were believed to come along much later since it was thought that any element heavier than helium had to originate in the cores of stars rather than being formed during the Big bang itself.
Clearly, stars did not come into existence contemporaneously with the Big Bang. The earliest stars took some time to form, go through their stellar life-cycle and eventually die over timescales of billions of years. Consequently, the presumption was that oxygen atoms similarly took eons to disperse throughout the Universe, some of them attaching to hydrogen atoms to produce the first interstellar “water.”
But the latest research, published in Astrophysical Journal Letters, demonstrates that our Universe’s first “water supplies” may have formed at a much earlier stage in the Universe’s history. The research suggests water formed less than one billion years after the Big Bang. That may seem like ages but in cosmic terms it represents just one-twentieth (5 percent) of the Universe’s current age.
Lead author of the study, PhD student Shmuel Bialy, of the Department of Astrophysics at Tel Aviv University’s School of Physics and Astronomy, commented,
“Our theoretical model predicts that significant amounts of water vapor could form in molecular clouds in young galaxies, even though these clouds bear thousands of times less oxygen than that in our own galaxy today,” adding, “This was very surprising and raises important questions about the habitability of the first planets, because water is the key component of life as we know it.”
According to the researchers, this timing for the formation of water in the universe has important implications in ascertaining when life itself began. Be it plant or animal life, water is essential for life to come about. It’s also essential for life to flourish. In living organisms, water is used both as a solvent to dissolve other compounds and in a host of metabolic processes.
Water formed in abundance despite dearth of materials
The researchers looked at the chemical reactions that led to the formation of water within the oxygen-poor environment of early molecular clouds. At a temperature of around 80 degrees Fahrenheit (about 27 degrees Celsius), water formation became highly efficient with abundant water forming despite the relative lack of raw materials.
“The universe then was warmer than today and gas clouds were unable to cool effectively,” said Professor Amiel Sternberg, also based at TAU. His colleague Professor Avi Loeb added, “Indeed the glow of the cosmic microwave background was hotter, and gas densities were higher.”
Water molecules are broken down by the ultraviolet light from stars. That being so, equilibrium as between “new” water formation and the destruction of “old” water can only be attained after hundreds of millions of years. But, importantly, the researchers found that this equilibrium in the early universe was similar to that measured in the today’s universe.
“We found it’s possible to build up significant quantities of water in the gas phase without much enrichment in heavy elements,” said Bialy. “In this current work, we calculated how much water could exist in the gas phase within molecular clouds that would form later generations of stars and planets.”
The researchers intend continuing their study to examine how much water could have existed as interstellar ice, as in our own Milky Way galaxy, and what fraction of all the water might actually be incorporated into newly-forming planetary systems.
