Astronomers using the NASA/ESA/CSA James Webb Space Telescope have discovered chemical fingerprints of primordial stars weighing between 1,000 and 10,000 times the mass of the Sun in GS 3073, an early galaxy at redshift of 5.55 (one billion years after the Big Bang).
A primordial supermassive star in the early Universe. Image credit: Gemini AI.
In 2022, astronomers predicted that supermassive stars naturally formed in rare, turbulent streams of cold gas in the early Universe, explaining how quasars could exist less than a billion years after the Big Bang.
“Our latest discovery helps solve a 20-year cosmic mystery,” said Dr. Daniel Whalen, an astronomer at the University of Portsmouth.
“With GS 3073, we have the first observational evidence that these monster stars existed.”
“These cosmic giants would have burned brilliantly for a brief time before collapsing into massive black holes, leaving behind the chemical signatures we can detect billions of years later.”
“A bit like dinosaurs on Earth, they were enormous and primitive. And they had short lives, living for just a quarter of a million years, a cosmic blink of an eye.”
The key to the discovery was measuring the ratio of nitrogen to oxygen in the GS 3073 galaxy.
The galaxy contains a nitrogen-to-oxygen ratio of 0.46, far higher than can be explained by any known type of star or stellar explosion.
“Chemical abundances act like a cosmic fingerprint, and the pattern in GS 3073 is unlike anything ordinary stars can produce,” said Dr. Devesh Nandal, an astronomer at the University of Virginia and the Harvard and Smithsonian’s Center for Astrophysics.
“Its extreme nitrogen matches only one kind of source we know of: primordial stars thousands of times more massive than our Sun.”
“This tells us the first generation of stars included truly supermassive objects that helped shape the early galaxies and may have seeded today’s supermassive black holes.”
The researchers modeled how stars between 1,000 and 10,000 solar masses evolve and what elements they produce.
They found a specific mechanism that creates massive amounts of nitrogen: (i) these enormous stars burn helium in their cores, producing carbon; (ii) carbon leaks into a surrounding shell where hydrogen is burning; (iii) carbon combines with hydrogen to create nitrogen through the carbon/nitrogen/oxygen (CNO) cycle; (iv) convection currents distribute the nitrogen throughout the star; and (v) eventually, this nitrogen-rich material is shed into space, enriching the surrounding gas.
The process continues for millions of years during the star’s helium-burning phase, creating the nitrogen excess observed in GS 3073.
The team’s models also predict what happens when these monster stars die — they don’t explode; instead, they collapse directly into massive black holes weighing thousands of solar masses.
Interestingly, GS 3073 contains an actively feeding black hole at its center, potentially the very remnant of one of these supermassive first stars.
If confirmed, this would solve two mysteries at once: where the nitrogen came from and how the black hole formed.
The study also found that this nitrogen signature only appears in a specific mass range.
“Stars smaller than 1,000 solar masses or larger than 10,000 solar masses don’t produce the right chemical pattern for the signature, suggesting a ‘sweet spot’ for this type of enrichment,” the scientists said.
The study was published in the Astrophysical Journal Letters.
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Devesh Nandal et al. 2025. 1000-10,000 MSun Primordial Stars Created the Nitrogen Excess in GS 3073 at z = 5.55. ApJL 994, L11; doi: 10.3847/2041-8213/ae1a63