Water vapor could have been just as abundant in cosmic molecular clouds a billion years after the Big Bang as it is today, says a group of researchers led by Dr Avi Loeb of the Harvard-Smithsonian Center for Astrophysics.
Composed of gas and dust, this molecular cloud resides in a stellar nursery called the Carina Nebula, located 7,500 light-years away in the constellation Carina. Image credit: NASA / ESA / Hubble SM4 ERO Team.
Dr Loeb and his colleagues examined the chemical reactions that could lead to the formation of water within the oxygen-poor environment of early molecular clouds.
“We looked at the chemistry within young molecular clouds containing a thousand times less oxygen than our Sun,” said Dr Loeb, who is the senior author on the paper accepted for publication in the Astrophysical Journal Letters (arXiv.org preprint).
“To our surprise, we found we can get as much water vapor as we see in our own Galaxy.”
The scientists found that at temperatures around 80 degrees Fahrenheit (300 K), abundant water could form in the gas phase despite the relative lack of raw materials.
“These temperatures are likely because the Universe then was warmer than today and the gas was unable to cool effectively,” said lead author Shmuel Bialy of Tel Aviv University, Israel.
“The glow of the cosmic microwave background was hotter, and gas densities were higher,” added Dr Amiel Sternberg, also from Tel Aviv University.
Although UV light from stars would break apart water molecules, after hundreds of millions of years an equilibrium could be reached between water formation and destruction.
The scientists found that equilibrium to be similar to levels of water vapor seen in the local Universe.
“You can build up significant quantities of water in the gas phase even without much enrichment in heavy elements,” Bialy said.
The results of the study might have interesting implications for the question of how early could have life originated in the Universe.
“Our study addresses the first step of water formation in early enriched, molecular gas clouds. If such a cloud is to collapse and form a protoplanetary disk, some of the water may make its way to the surfaces of forming planets,” the scientists wrote in the paper.
“However, the question of to what extent the water molecules that were formed in the initial molecular clouds, are preserved all the way through the process of planet formation, is beyond the scope of this paper.”
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Shmuel Bialy et al. 2015. Water Formation During the Epoch of First Metal Enrichment. ApJ Letters, accepted for publication; arXiv: 1503.03475
