In a study utilizing the James Webb Space Telescope (JWST), an international team of astronomers, led by the University of Cambridge, has observed a very young galaxy in the early universe, revealing surprising amounts of carbon. This discovery challenges current understanding of the formation and evolution of galaxies and the elements within them.

In astronomical terms, elements heavier than hydrogen or helium are classified as metals. The early universe primarily consisted of hydrogen, with minor amounts of helium and trace amounts of lithium. Every other element was forged in the hearts of stars and distributed across galaxies through stellar explosions known as supernovas. This process enriched the universe with metals, eventually leading to the formation of rocky planets and, ultimately, life as we know it.

The very first stars are the holy grail of chemical evolution, said Dr. Francesco D’Eugenio from the Kavli Institute for Cosmology at Cambridge, the study’s lead author. Since they are made only of primordial elements, they behave very differently from modern stars. By studying the formation of the first metals, we can set a timeline for the earliest steps leading to the formation of life.

Carbon, a key element in the universe’s evolution, plays a crucial role in forming grains of dust that clump together to create the first planetesimals and eventually planets. It is also essential for the formation of life on Earth. Previous research suggested that substantial amounts of carbon began forming about one billion years after the Big Bang. However, the recent findings indicate that carbon formed much earlier, potentially making it the oldest metal in the universe.

One of these galaxies, JADES-GS-z14-0 (shown in the extract), was found to be at a redshift of 14.32 (+0.08/-0.20), making it the most distant galaxy known so far. This corresponds to less than 300 million years after the Big Bang. In the background image, the blue represents light at 0.9, 1.15 and 1.5 micrometres.
One of these galaxies, JADES-GS-z14-0 (shown in the extract), was found to be at a redshift of 14.32 (+0.08/-0.20), making it the most distant galaxy known so far. This corresponds to less than 300 million years after the Big Bang. In the background image, the blue represents light at 0.9, 1.15 and 1.5 micrometres. Credit: Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA) / NASA, ESA, CSA, STScI

The team observed a very distant galaxy, one of the most distant yet detected, dating back to just 350 million years after the Big Bang, over 13 billion years ago. This galaxy is compact and low in mass, about 100,000 times less massive than the Milky Way. It’s just an embryo of a galaxy when we observe it, but it could evolve into something quite big, about the size of the Milky Way, noted D’Eugenio. But for such a young galaxy, it’s fairly massive.

Using Webb’s Near Infrared Spectrograph (NIRSpec), the researchers broke down the light from the young galaxy into a spectrum of colors. Each element leaves a distinct chemical fingerprint in the galaxy’s spectrum, enabling the team to determine its chemical composition. The analysis confidently detected carbon and tentatively identified oxygen and neon, pending further observations to confirm these elements.

We were surprised to see carbon so early in the universe since it was thought that the earliest stars produced much more oxygen than carbon, said co-author Professor Roberto Maiolino, also from the Kavli Institute. We had thought that carbon was enriched much later through entirely different processes, but its early appearance suggests that the first stars may have behaved very differently.

One model proposes that the earliest stars, upon exploding as supernovas, released less energy than expected. In this scenario, carbon, located in the stars’ outer shell and less gravitationally bound than oxygen, could have escaped more easily and spread throughout the galaxy, while much of the oxygen fell back and collapsed into black holes.

These observations tell us that carbon can be enriched quickly in the early universe, said D’Eugenio. Because carbon is fundamental to life as we know it, it’s possible that life didn’t necessarily evolve much later in the universe. Life might have emerged much earlier, although it may have evolved very differently than it did here on Earth.

This discovery opens up possibilities regarding the timeline for the emergence of life, suggesting that life might have arisen much earlier in the cosmos than previously thought.

Sources

University of Cambridge | Francesco D’Eugenio et al. JADES: Carbon enrichment 350 Myr after the Big Bang. Astronomy & Astrophysics. DOI: 10.48550/arXiv.2311.09908

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