It is now thought that water first formed in space only 100 to 200 million years after the Big Bang—billions of years earlier than previous estimates.
Simulations showed that oxygen created by primordial stars first fused with hydrogen in space when those stars exploded into supernovae.
Planets that emerged from the molecular clouds left behind by those early supernovae might have had habitable conditions because of the presence of water in those clouds.
Life (at least as we know it) requires water. Maybe there are life-forms out there that can survive without it, but so far, nobody knows what may be creeping around on distant exoplanets. So, as far as we know for sure, that first statement stands.
And because of that, the earlier water appeared in space, the earlier life could have hypothetically crawled out of somewhere. Now, a team of researchers—led by astrophysicist Daniel Whalen of the University of Portsmouth in England—has found that the first molecules of water may have formed billions of years before we thought they did. By running simulations of the early universe, Whalen showed that water could have been created by nuclear fusion in the cores of the oldest dying stars only 100 to 200 million years after the Big Bang.
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Few elements survived the intensity of the Big Bang. The lighter elements that did make it were hydrogen (one component of water), helium, lithium, and scant traces of barium and boron. Water, then, actually came from stars. Population III stars—also known as Pop III stars or primordial stars—are the oldest stars in the universe, and have still eluded even our most powerful telescopes. Before they burned themselves out and exploded into supernovae, there was no oxygen in the universe. And water cannot exist without oxygen.
“Primordial supernovae were the first nucleosynthetic engines in the universe, and they forged the heavy elements required for the later formation of planets and life,” Whalen and his team said in a study recently published in the journal Nature Astronomy.
While even the supernovae of Pop III stars are so ancient that none have been detected, simulations of two possible types of primordial supernovae (core-collapse and pair-instability supernovae) showed how water was likely synthesized in the nascent universe.
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After massive stars (over 10 solar masses) have fused all their hydrogen nuclei in their cores into helium, fused their helium into heavier elements, and fused some of those into even heavier elements, they explode into supernovae. Both core-collapse and pair-instability supernovae eject heavier elements, including oxygen, into space (though, a pair-instability supernova produces much higher amounts of those elements). Whalen’s simulations showed that huge molecular clouds formed in the supernova aftermath. As these clouds expanded and then cooled, oxygen in the haloes of the clouds reacted with hydrogen to create water. Later, much more water formed in the clouds’ dense core.
Stars and planets are thought to be born in protoplanetary disks that take shape in the superdense gas of molecular cloud cores, which means it is possible that the water present in those clouds might have given some early planets habitable conditions. That said, there are, of course, many other factors that determine habitability. How the earliest planets were affected by cosmic radiation and other factors remains unknown.
“[Water was] highly concentrated in the only structures capable of forming stars and planets,” Whalen said in a press release. “And that suggests that planetary disks rich in water could form at cosmic dawn, before even the first galaxies.”
If water finds a way, maybe life does, too.
Lettermark
Elizabeth Rayne is a creature who writes. Her work has appeared in Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.