Astronomers have discovered carbon in a galaxy observed just 350 million years after the big bang, in observations that raise the possibility that the conditions for life have been present almost since the dawn of time.
The observations, made by the James Webb Space Telescope, suggest that large amounts of carbon were released when the first generation of stars exploded in supernovae. Carbon is known to have seeded the first planets and is a building block for life as we know it, but was previously thought to have appeared much later in cosmic history.
“This is the earliest detection of an element heavier than hydrogen ever obtained,” said Prof Roberto Maiolino, an astronomer at the University of Cambridge and a co-author of the findings. “It’s a massive breakthrough.”
“The discovery of such a large amount of carbon in such a distant galaxy implies that life may have emerged very early in the universe, very close to the cosmic dawn.”
The very early universe was almost entirely composed of hydrogen, helium and small amounts of lithium. Every other element – including those that formed Earth and humans – was formed in stars and released during supernovae, when stars explode at the end of their lives. With each new generation of stars, the universe was enriched with progressively heavier elements until the rocky planets formed and life became possible.
Carbon is a key element in this process, as it can accumulate in dust grains in a rotating disk around stars, eventually being ejected into the earliest planets. It was previously thought that carbon enrichment occurred about 1 billion years after the big bang.
The latest research dates the earliest carbon fingerprint to just 350 million years, suggesting that carbon was released in large quantities in the supernovae of the first generation of stars in the universe. This does not change estimates of when life began on Earth, about 3.7 billion years ago, but it does suggest that some of the criteria for life appearing elsewhere in the universe were present much earlier than expected.
“The first stars are the holy grail of chemical evolution, as they consist only of primordial elements, and they behave very differently from modern stars,” said Dr Francesco D’Eugenio, an astrophysicist at the Kavli Institute for Cosmology in Cambridge and. lead author of the findings. “By studying how and when the first metals formed inside stars, we can establish a time frame for the earliest steps on the path that led to the formation of life.”
The galaxy, which is the fifth most distant ever observed, is small and compact – about 100,000 times smaller than the Milky Way. “It’s just an embryo of a galaxy when we observe it, but it could evolve into something quite large, the size of the Milky Way,” D’Eugenio said. “But for such a young galaxy, it’s pretty massive.”
An analysis of the spectrum of light coming from the galaxy yielded a confident detection of carbon and preliminary detections of oxygen and neon. “From carbon to DNA is a long journey, but it shows that the key elements are, in principle, already there,” Maiolino said.
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Dr Rafael Alves Batista, an astrophysicist at Sorbonne University, Paris, who was not involved in the latest findings, said: “The result is a big step forward and it’s something we didn’t know before.”
However, he said it was not possible to extrapolate from the discovery of carbon the likelihood of the emergence of life. “That’s not a jump I would make,” he said. “Most of these [early] stars are very massive so they die very quickly. Even if there are planets, I’m not very optimistic that they would have the conditions for life. The findings are very interesting, but I don’t think they are enough to solve anything.”
The findings will be published in the journal Astronomy & Astrophysics.
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