Was Water Abundant In The Early Universe?

This Hubble image features dark knots of gas and dust known as 'Bok globules,' which are dense pockets in larger molecular clouds / NASA, ESA, and The Hubble Heritage Team

With the search for water on other planets not harboring much success, it seems surreal that water can simply be found floating in space. By studying ancient dust clouds in the cosmos, astronomers have predicted that water appeared in the universe earlier than we thought. In fact, it may have formed only a billion years after the Big Bang. For comparison, our sun is predicted to be about 4.5 billion years old. The work has been accepted for publication in Astrophysical Journal Letters, and you can read the pre-print version here

It is intriguing that water may have formed so early on in the universe because it is a surprisingly complex molecule. The molecular makeup of water is two hydrogen atoms and one oxygen atom. Hydrogen is the simplest atom in the periodic table and not too complicated to make.

However, oxygen has an atomic number of eight, meaning that it contains eight protons in its core and eight neutrons. It is quite a sophisticated element and, for this reason, it only forms in the core of burning hot stars and couldn’t have formed during the chaos of the Big Bang.  

The length of time that it takes for stars to produce oxygen implies that star formation started fairly quickly after the Big Bang in order for oxygen to exist in the universe after 1 billion years. The oxygen then had to escape the burning star to cooler cosmic pastures. There are speculations that it was carried out of the stars by either surfing on stellar winds or from supernovae explosions (although this would have occurred sometime later).

Out in open space, these little hydrogen and oxygen atoms had to all collide with sufficient energy to chemically bond together and form water. You might think that overcoming all this strife would take a long time (scientists certainly thought so). Astrophysicist Avi Loeb from the Harvard-Smithsonian Center for Astrophysics commented on the discovery: “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.”

Even though the clouds were oxygen-poor, there’s still a good explanation for why water formed so readily in the early universe. "The universe then was warmer than today and the gas was unable to cool effectively," explains lead author and Ph.D. student Shmuel Bialy of Tel Aviv University. This warmer environment would be the perfect temperature to cook up water amongst the vacuum of space.

The reason the average temperature of the universe was warmer then than today (which is approx. 2.735 K, -270.42 °C, -454.76 °F) is explained by co-author Amiel Sternberg from Tel Aviv University: "The glow of the cosmic microwave background was hotter, and gas densities were higher." These factors made the universe more toasty!

It’s enthralling to think that water may have existed this early in the universe as it also happens to be at the heart of life as we know it. It is also interesting to discover that the early universe may have been brimming with a rich environment suitable for creating such a complex molecule.

[via Harvard-Smithsonian Center for Astrophysics, Discovery News]

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