Supermassive black holes, often billions of times the mass of our Sun, serve as the gravitational anchors at the centers of most galaxies, including our own Milky Way. When actively accreting matter, these cosmic behemoths blaze as quasars, some of the brightest and most energetic objects observable in the universe. Quasars emit copious radiation as gas and dust spiral inward, heated to extreme temperatures in their accretion disks. This light flickers irregularly as the black hole feeds, a phenomenon providing key insights into the dynamics of accretion and black hole growth. The detection of such flickering from one of the universe’s earliest quasars marks a significant milestone in astrophysics.

The quasar flicker detected by the MIT-led team represents the earliest known variability observed from such an object, emerging from what astronomers term the “cosmic dawn.” This period, occurring roughly 850 million years post-Big Bang, was thought to host only nascent galaxies and immature black holes. Contradicting previous assumptions, the observed quasar exhibited variability patterns similar to those found in more contemporary quasars, suggesting that the physical processes governing black hole accretion were already established at these primordial times.

Gene Leung, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research, explains that prior detections of quasars from the early universe showed bright, steady light sources but lacked the tell-tale flickering patterns that reveal underlying accretion processes. The detection of flicker is critical because it directly relates to fluctuations in how material is ingested by the black hole. Such fluctuations imprint themselves in the light output, encoding information about the accretion disk’s geometry and the feeding mechanisms at work.

Unexpectedly, the flickering quasar’s accretion disk appeared surprisingly flat and thin, resembling a “pancake” rather than the puffier, chaotic structures anticipated for black holes at such early stages of growth. This finding puzzles astronomers, as conventional wisdom suggests that youthful black holes in the young universe should exhibit turbulent, unstable accretion disks, reflecting ongoing rapid growth phases. Instead, this quasar’s disk mirrors the more orderly structures typically associated with mature, settled black holes.

Anna-Christina Eilers, an assistant professor of physics at MIT and a co-author on the study, interprets this evidence as suggesting that the tumultuous, rapid growth stages of supermassive black holes precede the luminous quasar phase visible to current telescopes. In other words, the messy early feeding epochs might occur so swiftly and early that by the time we observe the quasar’s brilliant light, the black hole’s accretion disk has already stabilized into a flat, well-organized structure.

This revelation adds to one of cosmology’s deepest enigmas: How did supermassive black holes form and reach immense mass so quickly in the early universe? The presence of such sophisticated accretion disks at cosmic dawn implies that significant growth and structural organization happened on remarkably short timescales, challenging existing models of black hole evolution and opening new avenues for theoretical and observational research.

Detecting flickering from such a distant quasar was a formidable technical challenge. Owing to cosmic expansion, the quasar’s emitted light is not only stretched to longer, infrared wavelengths — a phenomenon known as redshift — but its temporal flickering expands correspondingly. What might be a variation over weeks in the quasar’s frame becomes a gradual fluctuation observed over many months or years from Earth. This necessitated infrared observations over extended durations with high sensitivity.

The team turned to data collected by NASA’s NEOWISE mission, a space-based infrared survey telescope with a 14-year archive monitoring the entire sky at infrared wavelengths. High-quality, time-resolved infrared data provided the ideal dataset to detect the subtle, long-term flickering signal from the distant quasar. Utilizing refined data processing techniques developed by former MIT postdoc Kishalay De, now at Columbia University, the researchers extracted the earliest evidence of quasar variability from the cosmic dawn.

The flickering exhibited stochastic variations in brightness by up to 20 percent, equivalent to luminosity shifts of approximately 2 trillion times that of our Sun. Such variations imply fluctuating accretion rates and provide a rare glimpse into the black hole’s feeding habits in an epoch close to the universe’s infancy. By analyzing flicker behavior across multiple wavelengths, the researchers could infer temperature gradients within the disk, enabling them to map its structure and confirm its thin, flat morphology.

This discovery not only underscores that the physical mechanics of black hole accretion recognized in the modern universe were already in place shortly after the Big Bang but also poses profound implications for models of galaxy and black hole coevolution. Supermassive black holes exert powerful influence on their host galaxies, regulating star formation and galactic growth through energetic feedback processes. Understanding how early black holes matured thus impacts our grasp of galaxy formation and evolution across cosmic time.

Looking ahead, the team aims to push observational boundaries even further, seeking to identify flickering quasars at even earlier times. Capturing the nascent stages of black hole development promises to unravel the initial phases of black hole assembly and accretion disk formation. Such insights will illuminate the conditions prevailing in the first billion years and potentially solve the mystery of how black holes achieved such enormous masses so rapidly after the dawn of the universe.

Funded in part by NASA, this study represents a collaborative effort between MIT Kavli and multiple global institutions. It advances our cosmic understanding through innovative reuse of archival data and sets a benchmark for future infrared time-domain surveys. The insights gained from this flickering quasar discovery herald a new era in the study of black hole physics, galaxy evolution, and the earliest chapters of cosmic history.

Written by Jennifer Chu, MIT News

Subject of Research: Early Universe Quasar Variability and Supermassive Black Hole Accretion Disk Structure

Article Title: “Discovery of Cosmic Dawn Quasar Variability and Early Accretion Disk Signatures”

News Publication Date: 2024

Web References: http://dx.doi.org/10.1038/s41550-026-02897-4

Image Credits: NASA/JPL-Caltech

Keywords

Quasar flickering, supermassive black holes, cosmic dawn, accretion disk, early universe, NEOWISE, infrared astronomy, black hole growth, galaxy evolution, cosmic redshift, astrophysics, variability detection

Quasars, the immensely luminous nuclei powered by gas spiraling into SMBHs, have historically been recognized as cosmic beacons, charting the growth of black holes across cosmic time. In the local universe, it has been well documented that their brightness changes over time across multiple wavelengths, frequently linked to turbulent accretion flows and the physical conditions of their accretion disks and coronae. Observing this behavior at early epochs, close to the universe’s infancy, has remained elusive due to limited observational sensitivity and the faintness of these objects billions of light-years away.

The recent study overcomes these challenges by leveraging state-of-the-art infrared and X-ray telescopes, enabling a detailed examination of a quasar that thrived within less than a billion years from the universe’s beginning. Infrared observations covered five distinct filters, effectively probing the quasar’s rest-frame ultraviolet and optical emission. These wavelengths emanate primarily from the accretion disk itself, where matter spirals inward before ultimately plunging into the black hole. In tandem, X-ray data explored variability emanating from the quasar’s corona—an extremely hot, diffuse plasma enveloping the disk and responsible for high-energy emission.

Crucially, the team’s multiwavelength approach offers a rare glimpse into the spatial structure of the accretion flow. The variability spectrum reveals that, even in these early epochs marked by rapid mass accretion at high Eddington ratios, the disk retains a geometrically thin but optically thick form—a fundamental characteristic predicted by classical accretion disk theory. This finding challenges alternative models proposing more chaotic or thick disk geometries under such extreme conditions, thus refining our theoretical understanding of early SMBH fueling mechanisms.

Moreover, the signature of variability provides a powerful diagnostic tool, opening avenues to estimate SMBH masses directly during these formative epochs. Until now, mass measurements of early SMBHs primarily relied on indirect scaling relations or assumptions anchored in local analogues. The ability to track brightness fluctuations across wavelengths enables dynamic modeling of the accretion disk structure and its physical parameters, marking a pivotal step toward constructing an empirical census of SMBH growth across cosmic history.

From a broader perspective, this discovery exemplifies the increasing synergy between observational astronomy and theoretical models in unraveling the mysteries of the early universe. The findings not only affirm the existence of stable, thin accretion disks at high redshift but also validate variability as a promising observable in the study of primordial quasars. Observational constraints emerging from these data impose stringent limits on black hole feeding mechanisms operating under intense gravitational and radiative environments at the dawn of cosmic time.

In anticipation of next-generation observatories, such as the Rubin Observatory and the Roman Space Telescope, which promise to identify thousands of high-redshift quasars through sensitive time-domain surveys, the implications of this study are profound. These facilities will enable population-level investigations into the variability patterns of early SMBHs, exponentially increasing the statistical leverage to refine accretion physics models and improve SMBH mass estimates across cosmic epochs.

Understanding the nature of early quasar variability also has bearings on the broader cosmological landscape, where growing SMBHs influence galaxy evolution through energetic feedback processes. The heating and ionization of surrounding gas mediated by quasar emission impact star formation and the intergalactic medium, connecting SMBH growth to large-scale cosmic structure. Hence, observationally deciphering the accretion dynamics at cosmic dawn paves the way for more accurate models of galaxy formation and evolution.

Conventional wisdom had posited that early quasar accretion disks might be unstable or geometrically distorted due to the copious inflows feeding these nascent SMBHs at near-Eddington or super-Eddington rates. However, the detected variability and spectral signatures support a scenario where classical thin disk models remain valid, implying relatively orderly accretion despite the quasar’s extreme luminosity and young cosmic age. This clarification tightens the link between local and distant quasar phenomena, underscoring a universal mechanism governing SMBH growth.

Furthermore, the disentanglement of emission components from the disk and corona through simultaneous infrared and X-ray variability measurements offers a comprehensive portrait of the accretion environment. This dual-wavelength approach not only helps characterize the geometry and physical conditions in each region but also constrains the energy transfer processes between the disk and corona, crucial for explaining quasar emission mechanisms across the electromagnetic spectrum.

Intriguingly, the study’s results highlight the importance of variability as a complementary probe alongside traditional spectroscopic and photometric techniques. While spectral line studies remain indispensable for redshift and chemical composition determinations, variability provides temporal information that can uniquely inform us about dynamical processes in the quasar vicinity. As a consequence, time-domain astrophysics emerges as an increasingly central methodology for unlocking cosmic evolution’s secrets.

The timing and amplitude of the variability trends observed challenge theoretical uncertainties regarding the stability and lifetime of accretion disks in burgeoning quasars. They suggest persistent, coherent accretion episodes capable of sustaining rapid black hole growth over extended periods, a finding critical to explaining how SMBHs attained billion-solar-mass scales in under a billion years after the Big Bang.

This advance also opens important questions about the interplay of environmental factors shaping early SMBH evolution. The influence of intense radiation, inflows from surrounding dense gas reservoirs, and potential interactions with nascent stars and galaxies all factor into regulating accretion variability patterns. Future surveys targeting large samples will be paramount in disentangling these complex dependencies.

In conclusion, the detection of multiwavelength infrared and X-ray variability in one of the earliest-known quasars stands as a landmark achievement in observational cosmology. It crystallizes the utility of variability studies as a direct window into SMBH feeding processes, enabling precise constraints on accretion disk properties at epochs hitherto inaccessible. With a rapidly expanding arsenal of space- and ground-based observatories on the horizon, these pioneering measurements lay the groundwork for a new era in our quest to understand the formation and growth of the universe’s most enigmatic giants.

The implications of this discovery reverberate through multiple domains—from theoretical astrophysics to cosmology—ultimately enriching our comprehension of the universe’s formative years. As observational capabilities continue to advance, we can anticipate an explosion of discoveries that will illuminate the lifecycle of early SMBHs and their profound influence on cosmic history, transcending previous limitations and transforming our cosmic perspective forever.

Subject of Research: Early supermassive black hole accretion and quasar variability at high redshift.

Article Title: Discovery of quasar variability and early accretion disk signatures at cosmic dawn.

Article References:
Leung, G.C.K., Eilers, A.C., Panagiotou, C. et al. Discovery of quasar variability and early accretion disk signatures at cosmic dawn. Nat Astron (2026). https://doi.org/10.1038/s41550-026-02897-4

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41550-026-02897-4