A paramount enigma that the James Webb Space Telescope (JWST) was engineered to unravel pertains to the genesis of supermassive black holes (SMBHs).
For over two decades, cosmologists have grappled with the question of how celestial bodies of such immense gravitational influence – boasting masses equivalent to millions or even billions of Suns – could have materialized less than a billion years subsequent to the Big Bang. Standard cosmological paradigms posit that sufficiently massive black holes lacked the temporal window to form through conventional accretion or merger processes.
Emerging observational data has begun to challenge these prevailing models, lending credence to an alternative hypothesis: that the foundational ‘seeds’ of SMBHs originated directly from the gravitational collapse of vast clouds of interstellar gas, a phenomenon referred to as direct collapse black holes (DCBHs).
The sole remaining viable explanation is the prior existence of exceptionally massive stars in the early cosmos (Population III stars), capable of leaving behind substantial black hole remnants.
Leveraging the capabilities of the JWST, an international consortium of researchers has unearthed the initial corroborating evidence for the theory that stellar entities of extraordinary magnitude, ranging from 1,000 to 10,000 solar masses, denoted as ‘monster stars,’ were indeed present in the nascent Universe.
This investigation was spearheaded by Devesh Nandal, a postdoctoral research fellow supported by the Swiss National Science Foundation, affiliated with the University of Virginia and the Institute for Theory and Computation (ITC) at the Harvard & Smithsonian Center for Astrophysics (CfA).
Collaborating alongside him were Daniel Whalen, a Senior Lecturer in Cosmology at the Institute of Cosmology and Gravitation (ICG) at the University of Portsmouth; Muhammad A. Latif, an astrophysicist from United Arab Emirates University (UAEU); and Alexander Heger, a research scientist from the School of Physics and Astronomy at Monash University.
The team meticulously analyzed the chemical signatures within GS 3073, a galaxy initially identified in 2022 by Latif, Whalen, and their associates from the Institute for Astronomy (IfA) at the University of Edinburgh, the University of Exeter, and the Herzberg Astronomy and Astrophysics Research Centre.
At the time of its discovery, the research group had noted an exceptionally high ratio of nitrogen to oxygen (0.46), far exceeding what could be attributed to any known stellar type or supernova event. This observation prompted their hypothesis that the earliest stars in the Universe, designated as Population III stars, may have formed from turbulent, cold gas flows a few hundred million years following the Big Bang.
Furthermore, they observed that GS 3073 harbors an actively accreting black hole at its core, potentially representing the remnant of one of these ‘monster stars.’ The existence of such massive stellar objects, they proposed, could elucidate JWST’s detection of multiple quasars that were active less than a billion years after the Big Bang.
These energetic phenomena, also identified as Active Galactic Nuclei (AGNs), are driven by SMBHs at galactic centers. These black holes accelerate infalling gas and dust to relativistic speeds, releasing immense quantities of energy and causing the central region to temporarily outshine all stars within the galactic disk.
In a University of Portsmouth press release, Nandal stated:
Chemical abundances serve as a unique cosmic identifier, and the elemental composition observed in GS3073 diverges significantly from what conventional stars can synthesize. Its pronounced nitrogen content aligns exclusively with a single known source: primordial stars thousands of times more massive than our Sun.
This finding implies that the inaugural stellar generations included truly colossal objects that played a crucial role in sculpting early galaxies and may have been the progenitors of today’s supermassive black holes.
To rigorously test this hypothesis, Latif, Whalen, and their research team developed computational models simulating the evolutionary pathways and chemical output of stars with masses between 1,000 and 10,000 solar masses. These simulations enabled them to pinpoint a specific astrophysical process capable of accounting for the observed nitrogen-to-oxygen ratio in GS3073.
The proposed mechanism involves ‘monster stars’ undergoing helium fusion in their cores, yielding carbon. This carbon then migrates to the outer layers where hydrogen fusion is occurring. There, the carbon reacts with hydrogen to form nitrogen, which is subsequently distributed throughout the stellar interior via convective processes and ultimately expelled into the surrounding interstellar medium.
This enrichment process continues for millions of years, as long as helium fusion persists in the core, saturating the surrounding gas cloud with nitrogen until the characteristic nitrogen-to-oxygen ratio is achieved. Crucially, the team’s predictive models indicate that these colossal stars do not terminate their existence in supernova explosions. Instead, they are theorized to undergo direct gravitational collapse into massive black holes, forming the ‘seeds’ of the SMBHs observed in the present epoch.
Furthermore, their analysis revealed that this specific nitrogen signature is absent in stars outside this mass range, whether smaller or larger. If substantiated, these findings would resolve two significant mysteries arising from prior JWST observations.
Moreover, these discoveries are furnishing invaluable insights into the Universe as it existed during the period between 380,000 and 1 billion years post-Big Bang, a phase colloquially termed the “Cosmic Dark Ages.”
Until very recently, this epoch of cosmic history remained largely inaccessible to astronomical study due to the extreme faintness of light originating from this era, rendering it undetectable by conventional instruments. The advent of advanced infrared observational technologies, such as those employed by the JWST, has finally enabled its exploration. The researchers anticipate that future sky surveys will identify additional galaxies exhibiting comparable nitrogen excesses, thereby facilitating a more thorough investigation into the potential existence of these ‘monster stars.’
“Our most recent breakthrough offers a solution to a mystery that has persisted for two decades,” stated Whalen. “In GS 3073, we possess the inaugural observational evidence confirming the existence of these colossal stars. These cosmic behemoths would have blazed with extraordinary intensity for a relatively brief period before succumbing to direct collapse into massive black holes, leaving behind the chemical imprints that we can detect across vast cosmic distances.”
“Consider them something akin to dinosaurs on Earth – immense and primitive in form. Their lifespans were likewise ephemeral, lasting only a quarter of a million years – a mere cosmic blink of an eye.”
This article was initially disseminated by Universe Today. The original publication can be accessed here.
