Astronomers using the NASA/ESA/CSA James Webb Space Telescope have detected chemical signatures of primordial stars weighing between 1,000 and 10,000 times the mass of the Sun in GS 3073, an early galaxy at redshift 5.55 (one billion years after the Big Bang).
In 2022, astronomers predicted that supermassive stars formed naturally in rare turbulent flows 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-old cosmic mystery,” said Dr Daniel Whalen, an astronomer at the University of Portsmouth.
“With GS 3073, we have the first observational evidence for the existence of these monster stars.”
“These cosmic giants would burn brightly for a short time before collapsing into massive black holes, leaving behind chemical signatures that we can detect billions of years later.”
“Like dinosaurs on Earth, they were huge and primitive. And they had a short lifespan, just a quarter of a million years, the cosmic blink of an eye.”
The key to the discovery was measuring the ratio of nitrogen and oxygen in the galaxy GS 3073.
The galaxy has a nitrogen to oxygen ratio of 0.46, much higher than can be explained by any known type of star or stellar explosion.
“Chemical abundance acts like a cosmic fingerprint, and the structure of GS 3073 is unlike anything ordinary stars can create,” said Dr. Devesh Nandal, an astronomer at the University of Virginia and the Harvard-Smithsonian Center for Astrophysics.
“Its extreme levels of nitrogen are consistent with only one source we know of: primordial stars thousands of times more massive than our Sun.”
“This tells us that the first generation of stars included truly supermassive objects that helped form early galaxies and may have given birth to today's supermassive black holes.”
The researchers modeled how stars with masses between 1,000 and 10,000 solar masses evolve and what elements they produce.
They found a special mechanism that creates huge amounts of nitrogen: (i) these huge stars burn helium in their cores, producing carbon; (ii) carbon leaks into the surrounding shell, where hydrogen burns; (iii) carbon combines with hydrogen to form nitrogen through the carbon/nitrogen/oxygen (CNO) cycle; (iv) convection currents distribute nitrogen throughout the star; and (v) this nitrogen-rich material is eventually released into space, enriching the surrounding gas.
This process continues for millions of years during the star's helium burning phase, creating the excess nitrogen observed in GS 3073.
The team's models also predict what will happen when these monster stars die—they don't explode; instead, they collapse directly into massive black holes weighing thousands of solar masses.
Interestingly, at the center of GS 3073 there is an actively feeding black hole, potentially the remnant of one of the first supermassive stars.
If this is confirmed, it will 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 certain mass range.
“Stars with masses less than 1,000 solar masses or masses greater than 10,000 solar masses do not produce the correct chemical structure for the signature, indicating a 'sweet spot' for this type of enrichment,” the scientists said.
study was published in Letters in an astrophysical journal.
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Devesh Nandal etc.. 2025. 1000-10,000 MSSun primordial stars created an excess of nitrogen in GS 3073 at z = 5.55. ApJL 994, L11; doi: 10.3847/2041-8213/ae1a63
