Euclid discovers the most ancient quasars in the universe, rewriting early cosmic history

The European Space Agency’s Euclid space telescope has found 31 previously unknown quasars from the earliest epochs of cosmic history, including two that now hold the record as the most ancient quasars ever observed. Their light began its journey when the universe was just 670 million years old, barely 5% of its current age, and has traveled more than 13 billion years to reach our detectors.

The results, led by Daming Yang of Leiden University and published on 6 July 2026 in Astronomy and Astrophysics, represent a fundamental shift in how astronomers study the primordial universe. Before Euclid, accumulating the first ten quasars at redshift 7 or above took the global astronomical community more than a decade. In a single year of survey operations, Euclid has more than doubled that count.

What quasars reveal about the infant universe

A quasar is not a permanent feature of a galaxy. It marks a brief, violent episode during which vast quantities of gas and dust spiral into a central supermassive black hole, releasing energy on a scale that can outshine the entire host galaxy by hundreds to thousands of times. Quasars are the most luminous persistent objects in the cosmos, and that extreme brightness is precisely what makes them detectable across such immense distances.

Finding quasars at redshifts above 7 means looking back into the first 770 million years after the Big Bang, a period that overlaps with the epoch of reionisation. During that transitional era, the universe shifted from a cold, opaque state dominated by neutral hydrogen, the so-called dark ages, to the hot, ionised environment that persists today. Quasars contributed to that transformation by flooding their surroundings with energetic ultraviolet photons capable of stripping electrons from hydrogen atoms.

The challenge has always been detection. At such extreme distances, quasar light is faint, heavily redshifted into the infrared, and easily confused with foreground cool stars in our own galaxy. Ground-based surveys have spent years isolating candidates one at a time. Euclid changes the equation by combining wide-area sky coverage, deep infrared sensitivity, and the sharp imaging that only a space-based platform can provide.

Two new record holders

Among the 31 new quasars, 12 have redshifts of 7 or above. The two most distant objects in the sample, designated EUCL J172902.75+641018.1 and EUCL J125308.55+705432.3, sit at redshifts of 7.77 and 7.69, respectively. Both surpass the previous record holder, a quasar at redshift 7.64 discovered in 2021.

A redshift of 7.77 places the first object at a time when the universe was approximately 670 million years old. At that stage, the large-scale cosmic web of filaments and voids was still assembling, and the first massive galaxies were only beginning to coalesce from the primordial density fluctuations seeded during inflation. The existence of a supermassive black hole luminous enough to power a quasar at that epoch places tight constraints on black hole formation and growth models.

The second quasar in the pair has already been followed up in detail by Silvia Belladitta and collaborators using additional observations. Their analysis reveals that the quasar is embedded in a dusty, gas-rich galaxy undergoing intense star formation, offering a rare glimpse at the environment surrounding an early supermassive black hole. This kind of host galaxy characterisation is essential for understanding whether the earliest black holes grew primarily through gas accretion, through mergers with other black holes, or through some combination of both channels.

From exceptional outliers to a meaningful census

The significance of the new sample extends beyond individual record-breakers. Previous high-redshift quasar surveys were biased toward the brightest, most extreme objects, the tip of the iceberg. Those outliers provided valuable data points but could not represent the broader population. Euclid’s sensitivity reaches far enough down the luminosity function to capture fainter quasars that were invisible to earlier campaigns.

The result is what the team describes as the first true census of quasars at the dawn of the universe. With a statistically meaningful sample, astronomers can begin to measure the quasar luminosity function at these redshifts, estimate the contribution of quasars to the reionisation photon budget, and test theoretical predictions about the number density of supermassive black holes in the early cosmos.

Antonio La Marca, an ESA Research Fellow in the Euclid team, emphasised the scale of the achievement. Discovering this many quasars at redshift 7 or above in a single survey cycle is unprecedented and positions Euclid as the leading instrument for high-redshift quasar science.

Euclid’s unique capabilities

Euclid launched in July 2023 and began routine science operations on 14 February 2024. The telescope carries two instruments: the VIS camera, which images in the visible band with a resolution comparable to the Hubble Space Telescope but over a much wider field, and the NISP instrument, which provides near-infrared photometry and slitless spectroscopy. The combination is particularly powerful for high-redshift work because the Lyman-alpha break, the spectral signature that identifies the most distant quasars, falls squarely in the near-infrared at redshifts above 6.

The 31 quasars reported in this study were extracted from the Euclid Wide Survey, which will eventually cover more than a third of the total sky. As the survey expands, the number of high-redshift quasars is expected to grow substantially, providing the statistical foundation for population studies that have never been possible before.

The data processing pipeline that made this discovery possible is itself a major collaborative effort. More than 2000 scientists and engineers in the Euclid Consortium, drawn from 300 institutions across 15 European countries, the United States, Canada, and Japan, contribute to the reduction, calibration, and analysis of the survey data. Identifying rare, extremely distant quasars in datasets containing billions of sources requires sophisticated machine learning classifiers trained on both simulated and observed quasar spectra, followed by spectroscopic confirmation from ground-based facilities.

Implications for black hole formation theory

The existence of billion-solar-mass black holes when the universe was less than a billion years old has been one of the most persistent puzzles in extragalactic astrophysics. Standard models of black hole growth through Eddington-limited gas accretion struggle to produce such massive objects in the available time unless the initial seeds were themselves very massive, on the order of tens of thousands of solar masses rather than the stellar-mass remnants left behind by the first generation of stars.

Proposed solutions include the direct collapse of pristine gas clouds into massive black hole seeds, runaway mergers in dense stellar clusters, and episodes of super-Eddington accretion during which the infall rate temporarily exceeds the radiation-pressure limit. Each scenario leaves different observational signatures in the properties of the quasar population, including the luminosity function slope, the black hole mass distribution, and the characteristics of the host galaxies.

With 31 new data points at redshifts between 6.6 and 7.8, the Euclid sample begins to provide the discriminating power needed to test these competing models. Future spectroscopic follow-up with facilities such as the James Webb Space Telescope and the ground-based Extremely Large Telescope will add black hole mass estimates and chemical abundance measurements to the picture, further sharpening the constraints.

A new chapter in observational cosmology

Euclid was designed primarily to investigate the nature of dark energy and dark matter by mapping the large-scale structure of the universe through weak gravitational lensing and galaxy clustering. The discovery of ancient quasars is a powerful demonstration that the mission’s scientific reach extends far beyond its original design parameters. By probing the most distant and luminous sources in the observable universe, Euclid connects the physics of black hole growth to the grand narrative of cosmic evolution, from the first light after the Big Bang to the accelerating expansion driven by dark energy.

The 31 quasars announced today are drawn from a fraction of the total survey area. As Euclid continues scanning the sky, the catalogue of primordial quasars will grow, each new detection adding a data point to the emerging statistical portrait of the universe in its first billion years. For the first time, the study of the earliest supermassive black holes is moving from the regime of individual discoveries to the regime of population science, and that transition marks a genuine turning point in observational cosmology.

© 2026 SKYCR.ORG | Homer Dávila Gutiérrez, FRAS. All rights reserved. Reproduction in whole or in part without express permission is prohibited. Original source: ESA/Euclid Consortium, Astronomy and Astrophysics (2026). DOI: 10.1051/0004-6361/202658883