What exactly is a quasar and how bright can they get?

A quasar is an extraordinarily luminous galactic core powered by a supermassive black hole actively consuming surrounding gas and dust. They can outshine entire galaxies containing hundreds of billions of stars. The energy comes from superheated material spiraling into the black hole through a rotating accretion disk, releasing massive amounts of radiation.

How far away is the quasar J0439+1634 and when did its light originate?

The light we detect from J0439+1634 left its source roughly 850 million years after the Big Bang, making it one of the earliest quasars ever observed. Given the Universe is approximately 13.8 billion years old, we are essentially glimpsing a cosmic object from when the Universe was only about 6% of its current age.

Why do quasars flicker, and what does the flickering tell scientists?

Quasar flickering, called variability, reflects real physical changes in the accretion disk — shifting infall rates of gas, magnetic turbulence, and thermal fluctuations. Scientists use these brightness changes as a diagnostic tool, the way a doctor reads a heartbeat, to measure the disk's size, temperature, and overall structure around the central black hole.

Why is it surprising that this ancient quasar has a well-organized accretion disk?

Just 850 million years post-Big Bang, the Universe was a chaotic, rapidly expanding environment. Discovering a flat, stable, pancake-shaped accretion disk — a feature typical of much older, mature quasars — challenges our understanding of how quickly supermassive black holes could organize and grow structured feeding mechanisms in such early cosmic conditions.

Has flickering ever been detected in quasars this old before?

No — J0439+1634 marks the first confirmed detection of flickering in a quasar from the cosmic dawn era. While astronomers have catalogued many ancient quasars before, observing actual brightness variability in one this distant and old is entirely unprecedented, opening a brand-new way to study early Universe black holes.

What are relativistic jets and do all quasars produce them?

Relativistic jets are powerful beams of energized plasma launched at near-light-speed perpendicular to a quasar's accretion disk, stretching thousands of light-years into surrounding space. Not all quasars produce them — only a fraction, sometimes called radio-loud quasars, generate these dramatic structures, which are thought to influence the evolution of surrounding galaxies.

A Quasar at Cosmic Dawn Flickers into View

In a remarkable window into the infant Universe, astronomers have detected a flickering quasar — designated J0439+1634 — as it appeared a mere 850 million years after the Big Bang. This landmark discovery, led by researchers at MIT's Kavli Institute for Astrophysics and Space Research, raises profound new questions about how supermassive black holes formed, fed, and matured so rapidly in the cosmos's earliest epoch. The fact that this ancient beacon of light was observed to flicker — something never before seen in a quasar from this era — has opened a stunning new diagnostic window into the physics of accretion at cosmic dawn.

The flickering light of this distant cosmic lighthouse revealed that the supermassive black hole at the heart of J0439+1634 harbors a flat, pancake-shaped accretion disk — a structure far more familiar in the quasars of the modern, well-evolved Universe. That recognition alone is enough to stop astrophysicists in their tracks. How could such an orderly, mature-looking structure exist so early in cosmic history, when the Universe itself was still a chaotic, rapidly expanding environment?

"Although there have been a lot of quasars found in the cosmic dawn, this is the first time we actually see one flickering." — Gene Leung, MIT Kavli Institute for Astrophysics and Space Research

What Is a Quasar, and Why Does It Flicker?

A quasar (short for quasi-stellar object) is one of the most energetic phenomena in the Universe. At its core lies a supermassive black hole — an object containing millions to billions of times the mass of our Sun — actively consuming surrounding material. An active black hole draws in gas and dust through a swirling, high-temperature structure known as an accretion disk. As this cosmic material spirals inward and falls toward the event horizon, it is compressed and heated to extreme temperatures, radiating an enormous amount of energy across the electromagnetic spectrum. In many quasars, powerful relativistic jets of energized plasma are launched perpendicular to the disk, streaming outward for thousands of light-years. The combined luminosity of all this activity is what we observe as the brilliant point of light we call a quasar — so bright it can outshine an entire galaxy of hundreds of billions of stars.

The flickering of a quasar — technically referred to as quasar variability — is not random noise. It is an intrinsic physical signal that encodes information about the structure and dynamics of the accretion disk. Changes in the rate at which material falls onto the black hole, magnetic turbulence within the disk, and thermal instabilities can all produce variations in the quasar's brightness over timescales ranging from days to years. Critically, the amplitude and timescale of this flickering allow astronomers to infer the size, geometry, and feeding state of the accretion disk — even across billions of light-years of space. Detecting this signal in the earliest known quasars is therefore a powerful new tool for understanding the origins of these extraordinary objects.

Supermassive Black Holes Across Cosmic Time

The quasar J0439+1634 first appeared in a Hubble Space Telescope (HST) image of a distant galaxy being gravitationally lensed by a foreground galaxy — a natural cosmic magnifying glass that made the distant object bright enough to study in detail. This view shows us what J0439+1634 looked like 12.8 billion years ago, only a brief moment after the Big Bang (13.8 billion years ago) in cosmic terms.

The supermassive black hole powering J0439+1634 is estimated to contain billions of solar masses of material — a colossal engine driving the extraordinary luminosity of the quasar. Yet it is the shape of the accretion disk that puzzles scientists most. Conventional theoretical models of black hole growth predict that in the very early Universe, black holes should be in a turbulent, rapidly growing state. Accretion disks during this phase are expected to be thick, puffy, and geometrically inflated — fed by chaotic, torrential infalls of gas. A thin, flat, geometrically settled accretion disk, by contrast, is a signature of a black hole that has already passed through that frenzied growth phase and entered a more stable, efficient accretion regime.

Finding exactly such a disk in J0439+1634 — at a cosmic epoch when the Universe was less than one-fifteenth of its current age — suggests that this black hole had already completed its turbulent adolescence and matured remarkably quickly.

"I think what this suggests is that all the messy, very rapid growth phases that we expect all black holes to go through at some point happen very, very early on, before we see them as these very bright luminous quasars. That's the picture that's emerging." — Anna-Christina Eilers, Assistant Professor of Physics, MIT

This is more than an academic curiosity. The activity of a supermassive black hole is deeply intertwined with the fate of its host galaxy. The powerful outflows of radiation and jets from an active galactic nucleus can heat and expel surrounding gas, quenching star formation across an entire galaxy — a process known as AGN feedback. Conversely, the compression of gas by these outflows can, under certain conditions, trigger new bursts of star formation. Over billions of years, this cosmic push-and-pull sculpts the morphology, stellar population, and chemical composition of the galaxy.

"Without supermassive black holes, no galaxy would look the way it does today. Black holes play a major role in shaping how galactic ecosystems look." — Anna-Christina Eilers, MIT

Spotting the Flicker Across 12.8 Billion Light-Years

Detecting the variability of a quasar at such extreme distances is a formidable observational challenge. At a cosmological redshift of approximately z ≈ 6.5, the light from J0439+1634 has been dramatically stretched by the expansion of the Universe. Ultraviolet and optical wavelengths emitted by the quasar's hot accretion disk are redshifted all the way into the near-infrared by the time they reach our telescopes. This means that standard optical surveys, optimized for nearby sources, are essentially blind to these objects.

To overcome this, the research team turned to data from the NEOWISE mission — a NASA space telescope that surveyed the entire sky in the mid-infrared for approximately 14 years. After carefully reprocessing and re-calibrating the archival data to extract the faintest possible signals, the team identified the telltale brightness variations of J0439+1634. The multi-year baseline of NEOWISE observations was essential: quasar variability at these redshifts is further stretched in time due to cosmological time dilation, meaning that intrinsic variations that might play out over months in the quasar's rest frame are observed to unfold over years from our vantage point.

The analysis yielded extraordinary numbers. The team estimated that J0439+1634 shines with the luminosity of approximately 12 trillion Suns, and that its flickering corresponds to brightness variations equivalent to roughly 2 trillion solar luminosities — a staggering swing in power output that underscores the violent physical processes occurring in the accretion disk. Detailed modeling of the variability signal allowed the team to reconstruct the geometry of the disk, confirming it to be thin and flat — consistent with a standard Shakura-Sunyaev disk geometry typically associated with mature, lower-redshift quasars.

Quasar designation: J0439+1634
Observed epoch: ~850 million years after the Big Bang (redshift z ≈ 6.5)
Lookback time: ~12.8 billion years
Total luminosity: ~12 trillion solar luminosities
Variability amplitude: ~2 trillion solar luminosities
Accretion disk geometry: Thin, flat (consistent with a mature standard disk)
Key instrument: NASA NEOWISE, 14-year infrared survey baseline
Detection significance: Earliest known flickering quasar ever observed

"This provides direct evidence that the same feeding processes and structures observed in the nearby Universe were already in place at very early times, despite very different cosmic environments, which had never been seen before." — Anna-Christina Eilers, MIT

The Bigger Picture: Galaxy Formation at Cosmic Dawn

To appreciate why this discovery is so significant, it helps to consider the broader context of galaxy formation in the early Universe. The prevailing Lambda Cold Dark Matter (ΛCDM) cosmological model predicts that the first galaxies began assembling within the first billion years after the Big Bang — seeded by tiny quantum fluctuations in the primordial density field that were amplified by dark matter into the first gravitational wells. Within these wells, ordinary matter condensed, cooled, and collapsed to form the first stars and protogalaxies.

We now know, from surveys conducted by the James Webb Space Telescope (JWST) and others, that more than 200 supermassive black holes have been identified in the Universe's first billion years. They appear as extraordinarily bright, compact sources — unmistakable signatures of active, rapidly growing black holes. Yet explaining how black holes of such enormous mass could have assembled so quickly remains one of the most pressing unsolved problems in modern astrophysics.

Proposed mechanisms for seeding supermassive black holes in the early Universe include:

Remnants of the first (Population III) stars: The first generation of massive, metal-free stars may have left behind black holes of tens to hundreds of solar masses, which then grew rapidly through mergers and accretion.
Direct collapse black holes (DCBHs): Under certain conditions, massive gas clouds in the early Universe may have bypassed the stellar stage entirely and collapsed directly into black holes of 10,000 to 100,000 solar masses — providing a more massive "seed" that could grow more quickly.
Primordial black holes: A more speculative scenario in which black holes formed in the density fluctuations of the very early Universe, before any stars or galaxies existed.

The maturity of J0439+1634's accretion disk is a critical constraint on these models. If the black hole already has a settled, thin disk at 850 million years post-Big Bang, it must have completed its chaotic, rapid-growth phase even earlier — potentially within the first few hundred million years of cosmic history, a period that remains largely unexplored even by JWST.

"This means something happened even earlier on that led to these systems to look so mature." — Gene Leung, MIT Kavli Institute for Astrophysics and Space Research

What Comes Next: Pushing Further Back in Cosmic History

The discovery of J0439+1634's variability opens a new chapter in the observational study of the early Universe. To understand what drove such rapid black hole maturation, astronomers need to peer even deeper into cosmic history — toward the Epoch of Reionization and beyond, to the epoch when the host galaxy of this quasar was first assembling itself from primordial gas. This is precisely the regime where instruments like JWST and, in the future, the ESA Euclid mission and the upcoming Nancy Grace Roman Space Telescope will be indispensable.

Future observations will aim to detect and characterize quasar variability at even higher redshifts — potentially catching black holes in the act of their earliest, most turbulent growth phases. Multi-wavelength campaigns combining infrared variability surveys with high-resolution spectroscopy from JWST could allow astronomers to directly measure the masses, spin rates, and accretion efficiencies of these primordial black holes, providing a far more detailed physical picture than luminosity alone can offer.

The story of J0439+1634 is, in many ways, a story about the Universe's surprising capacity to build complexity with breathtaking speed. In less than a billion years after the Big Bang — a cosmological eyeblink — the Universe had already assembled supermassive black holes, wrapped them in geometrically mature accretion disks, and set them to work shaping the galaxies around them. Understanding how this happened is not merely an academic exercise: it is a fundamental part of understanding how the Universe became the rich, structured cosmos we inhabit today.

Key Findings at a Glance

J0439+1634 is the earliest known flickering quasar, observed as it appeared 850 million years after the Big Bang.
Its accretion disk is thin and geometrically flat — a structure normally associated with mature, low-redshift quasars — suggesting early and rapid black hole maturation.
The quasar's variability was detected using 14 years of NEOWISE infrared survey data, with brightness variations of ~2 trillion solar luminosities.
The discovery implies that the black hole's chaotic rapid-growth phase occurred even earlier than 850 million years post-Big Bang, before it was visible as a bright quasar.
The result provides direct observational evidence that standard accretion disk physics was already operating in the early Universe, under very different cosmic conditions than today.
Understanding this system will require observations at even higher redshifts, pushing into the frontier of cosmic dawn science with next-generation observatories.

Ancient Pulsating Quasar Spotted from the Universe's Earliest Era