Astronomers have found 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.
Observations made by the James Webb Space Telescope show that vast amounts of carbon were released when the first generation of stars exploded in supernovae. Carbon is known to have spawned the first planets and is a building block for life as we know it, but it was previously thought to have appeared much later in cosmic history.
“This is the earliest detection of an element heavier than hydrogen ever discovered,” said Prof Roberto Maiolino, an astronomer at the University of Cambridge and co-author of the findings. “This is a huge discovery.”
“Finding a large amount of carbon in such a distant galaxy suggests that life could potentially have appeared very early in the universe, really 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—formed in stars and was 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 rocky planets formed and life became possible.
Carbon is an essential element in this process, as it can condense into dust grains in a rotating disk around the stars, eventually snowballing into the earliest planets. Previously, carbon enrichment was thought to have occurred about 1 billion years after the big bang.
The latest research dates the earliest carbon fingerprint to just 350 million years old, suggesting that carbon was released in large quantities in the supernovae of the first generation of stars in the universe. This does not change the estimate of the beginning of life on Earth, about 3.7 billion years ago, but it suggests that some of the criteria for the appearance of life elsewhere in the universe were present much earlier than expected.
“The first stars are the holy grail of chemical evolution because they are made only of primordial elements and 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 in stars, we can determine 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 develop into something quite large, the size of the Milky Way,” D’Eugenio said. “But for such a young galaxy, it’s pretty massive.”
Analysis of the spectrum of light coming from the galaxy yielded a confident detection of carbon and tentative detections of oxygen and neon. “From carbon to DNA is a huge journey, but it shows that these key elements are basically already there,” Maiolino said.
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Dr Rafael Alves Battista, an astrophysicist at Sorbonne University, Paris, who was not involved in the latest discoveries, said: “The result is a big leap forward and is something we did not know before.”
However, he said it was not possible to extrapolate from the discovery of carbon the probability of life arising. “It’s not a leap I would make,” he said. “Most of these [early] stars are too massive, so they die too quickly. Even if there were planets, I’m not very optimistic that there would be conditions for life. The findings are very interesting, but I don’t think they are enough to decide anything.
The findings are to be published in the journal Astronomy & Astrophysics.
