Using the James Webb Space Telescope, an international team of researchers led the Center for Astrophysics | Harvard & Smithsonian have discovered chemical fingerprints of gigantic primordial stars that were among the first to form after the Big Bang.
Cambridge, MA (December 9, 2025)— For two decades, astronomers have puzzled over how supermassive black holes, which are some of the brightest objects in the universe, could exist less than a billion years after the Big Bang. Normal stars simply couldn't create such massive black holes quickly enough.
Now, using NASA’s James Webb Space Telescope (JWST), an international team of astronomers has found the first compelling evidence that solves this cosmic mystery: “monster stars” weighing between 1,000 and 10,000 times the mass of our Sun existed in the early universe. The breakthrough came from examining chemical signatures in a galaxy called GS 3073.
A new study led by scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA) and the University of Portsmouth in England has discovered an extreme imbalance of nitrogen to oxygen that cannot be explained by any known type of star.
In 2022, researchers published work in Nature predicting that supermassive stars naturally formed in rare, turbulent streams of cold gas in the early universe, explaining how quasars (extraordinarily bright black holes) could exist less than a billion years after the Big Bang.
“Our latest discovery helps solve a 20-year cosmic mystery,” said Daniel Whalen from the University of Portsmouth's Institute of Cosmology and Gravitation. “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 GS 3073. 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.
Devesh Nandal, a Swiss National Science Foundation postdoctoral fellow at the CfA’s Institute for Theory and Computation said, “Chemical abundances act like a cosmic fingerprint, and the pattern in GS 3073 is unlike anything ordinary stars can produce. 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 eleme,brnts they produce. They found a specific mechanism that creates massive amounts of nitrogen:
Cambridge, MA (December 9, 2025)— For two decades, astronomers have puzzled over how supermassive black holes, which are some of the brightest objects in the universe, could exist less than a billion years after the Big Bang. Normal stars simply couldn't create such massive black holes quickly enough.
Now, using NASA’s James Webb Space Telescope (JWST), an international team of astronomers has found the first compelling evidence that solves this cosmic mystery: “monster stars” weighing between 1,000 and 10,000 times the mass of our Sun existed in the early universe. The breakthrough came from examining chemical signatures in a galaxy called GS 3073.
A new study led by scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA) and the University of Portsmouth in England has discovered an extreme imbalance of nitrogen to oxygen that cannot be explained by any known type of star.
In 2022, researchers published work in Nature predicting that supermassive stars naturally formed in rare, turbulent streams of cold gas in the early universe, explaining how quasars (extraordinarily bright black holes) could exist less than a billion years after the Big Bang.
“Our latest discovery helps solve a 20-year cosmic mystery,” said Daniel Whalen from the University of Portsmouth's Institute of Cosmology and Gravitation. “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 GS 3073. 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.
Devesh Nandal, a Swiss National Science Foundation postdoctoral fellow at the CfA’s Institute for Theory and Computation said, “Chemical abundances act like a cosmic fingerprint, and the pattern in GS 3073 is unlike anything ordinary stars can produce. 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 eleme,brnts they produce. They found a specific mechanism that creates massive amounts of nitrogen:
- These enormous stars burn helium in their cores, producing carbon;
- The carbon leaks into a surrounding shell where hydrogen is burning;
- The carbon combines with hydrogen to create nitrogen through the carbon/nitrogen/oxygen (CNO) cycle;
- Convection currents distribute the nitrogen throughout the star; and,
- 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 models, published in the Astrophysical Journal Letters, 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.
These findings open a new window into the universe's first few hundred million years, a period astronomers call the "cosmic Dark Ages" when the first stars ignited and began transforming the simple chemistry of the early universe into the rich variety of elements we see today.
The researchers predict that JWST will find more galaxies with similar nitrogen excesses as it continues surveying the early universe. Each new discovery will strengthen the case for these ultra-massive first stars.
The models, published in the Astrophysical Journal Letters, 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.
These findings open a new window into the universe's first few hundred million years, a period astronomers call the "cosmic Dark Ages" when the first stars ignited and began transforming the simple chemistry of the early universe into the rich variety of elements we see today.
The researchers predict that JWST will find more galaxies with similar nitrogen excesses as it continues surveying the early universe. Each new discovery will strengthen the case for these ultra-massive first stars.
Resource:
Nandal, D. et al, “1000-10,000 M ⊙ Primordial Stars Created the Nitrogen Excess in GS 3073 at z = 5.55,” The Astrophysical Journal Letters, doi: 10.3847/2041-8213/ae1a63
About the Center for Astrophysics | Harvard & Smithsonian
The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.
Media Contacts:
Amy C. Oliver, FRAS
Public Affairs Officer
Center for Astrophysics | Harvard & Smithsonian
+1 520 879 4406
amy.oliver@cfa.harvard.edu