Scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) have discovered that water vapor likely appeared in pockets across the universe a billion years after the Big Bang.
According to earlier theories, the formation of water in space may have taken a longer time since the oxygen created in the first stars had to disperse and combine with hydrogen molecules in significant amounts. The CfA study asserts that this process occurred earlier than initially thought.
"We looked at the chemistry within young molecular clouds containing a thousand times less oxygen than our Sun. To our surprise, we found we can get as much water vapor as we see in our own galaxy," Avi Loeb, an astrophysicist from the CfA, said.
Elements heavier than helium and hydrogen were missing during the initial stages of the universe. The earliest stars are believed to have been massive but short-lived. Those first generation stars produced elements such as oxygen, which eventually spread across the universe through supernova explosions and stellar winds. This phenomenon created gas enriched "islands" filled with heavy elements but poor in oxygen compared to gas found in modern-day Milky Way.
The CfA researchers studied chemical reactions that could cause the formation of water in early molecular clouds with poor oxygen content. They discovered that despite the lack of base materials, abundant water could form in these molecular clouds at 80 degrees Fahrenheit (300 Kelvin).
Shmuel Bialy, a Ph.D. student at the Tel Aviv University and lead author of the research, explained that this result is likely because the universe was warmer in its earlier stages compared to today, preventing the gas to effectively cool.
The study's co-author, Amiel Sternberg, added that the cosmic microwave glow back then was hotter, and that the densities of gases were higher.
It is believed that equilibrium between destruction and water formation could be achieved after hundreds of millions of years despite ultraviolet light from stars possibly breaking water molecules apart. The researchers found that this equilibrium is similar to the water vapor levels present in today's universe.
"You can build up significant quantities of water in the gas phase even without much enrichment in heavy elements," Bialy added.
The CfA research estimates the amount of water that could exist during the gas phase within molecular clouds, which will eventually create the stars and planets in later generations. The study, however, does not show how much water would be present in ice form, which could be found in most parts of the galaxy. Neither does it present the fraction of the water that would likely be included in the creation of new planetary systems.
The study is published in the journal Astrophysical Journal Letters.
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