Thirty-one newly discovered ancient quasars are giving scientists their clearest view yet of the universe’s earliest giant black holes.
Quasars are among the brightest objects in the universe, shining with the power of supermassive black holes consuming vast amounts of matter. Some are so luminous they outshine entire galaxies, allowing astronomers to see them across more than 13 billion years of cosmic history.
Now, an international team of scientists has discovered 31 of the oldest quasars ever found, including the two earliest known examples. These extraordinary objects were already blazing with the light of a trillion suns when the universe was only about 670 million years old. The discovery, published in Astronomy & Astrophysics, is providing one of the clearest views yet of the universe’s earliest chapter and raising new questions about how giant black holes formed so quickly after the Big Bang.
“These objects provide the best clues for understanding how supermassive black holes form,” said co-author Joseph Hennawi, a physics professor with joint appointments at UC Santa Barbara and Leiden University. “These monsters — weighing billions of times the mass of our sun — somehow already existed when the universe was in its infancy. We don’t yet have a good understanding of how they grew so massive, so fast.”
Hunting the Universe’s Earliest Quasars
Astronomers have spent decades searching for the first quasars because they offer a rare glimpse into the dawn of galaxies and the birth of supermassive black holes.
But finding them is incredibly difficult. Quasars that existed less than about 770 million years after the Big Bang are exceptionally rare because only a small number of galaxies had grown large enough to produce them. Even when they are present, their faint light can easily be mistaken for stars much closer to Earth.
The universe itself adds another challenge. As space expands, light from these ancient objects is stretched from ultraviolet into near-infrared wavelengths, an effect known as redshift. Unfortunately, these wavelengths overlap with the natural infrared glow of Earth’s atmosphere, making faint quasars extremely difficult to detect from ground-based telescopes. Astronomers use redshift to estimate both how far away an object is and how early it appeared in cosmic history.
“A redshift of 7 takes us to when the universe was just 750 million years old, less than 6% of its current age,” Hennawi said.
“These two things make finding quasars at these distances incredibly difficult,” said lead author Daming Yang, a doctoral student in Hennawi’s group at Leiden University. “For every one of them there are thousands of stars in our Milky Way and nearby galaxies that look almost identical in the imaging surveys. And since their light is stretched to the infrared at such distances, we need a survey that is both wide enough to capture these rare objects and deep enough to detect their faint light.”
From the ground, this search is nearly impossible. Scientists needed a telescope above Earth’s atmosphere.
Euclid Is Transforming the Search for Ancient Quasars
The European Space Agency launched the Euclid space telescope in 2023 to explore one of the least understood periods in cosmic history. Orbiting above Earth’s infrared haze, Euclid can detect faint objects across enormous areas of the sky that ground-based observatories cannot easily reach.
Using data from the Euclid Wide Survey, researchers uncovered an unprecedented 31 ancient quasars dating to a time when the universe was only about 5% of its current age. When the survey is complete, it will map more than one-third of the entire sky.
Before Euclid, astronomers had identified only a small number of exceptionally bright early quasars. That made it difficult to understand what the broader population of these ancient objects looked like.
“Euclid is a true game-changer,” Daming said. “Before, we could only find a handful of the very brightest ancient quasars, but Euclid lets us search far more efficiently across huge areas of sky to capture much fainter light. It’s a unique tool for quasar hunting.”
Giant Black Holes in the Infant Universe
Researchers have already taken a closer look at the second oldest quasar in the new sample. They found it sits inside a dusty, gas-rich galaxy undergoing intense star formation, offering a rare glimpse of what the homes of the earliest supermassive black holes may have looked like.
These quasars come from the epoch of reionization, a pivotal era when the first stars and galaxies transformed the universe by ionizing the neutral hydrogen that filled space after the Big Bang. This period laid the foundation for the universe we see today.
Of the 31 newly discovered quasars, 14 have redshifts of 7 or higher. The two oldest reached redshifts of 7.69 and 7.77, making them the earliest quasars ever observed. Their light has traveled for just over 13 billion years, revealing them as they appeared during the universe’s first 670 million years. They also surpass the previous distance record established by Hennawi’s team in 2021.
The record itself is only part of the story.
“Every step further back in time makes the puzzle more perplexing: How did the Universe produce supermassive black holes so quickly?” Hennawi said. “We’re finding black holes with hundreds of millions of times the mass of our sun at a time when the universe was barely getting started.”
Looking Back Even Farther in Time
Advances in telescope technology and data analysis are rapidly pushing astronomy deeper into the universe’s past. It took more than a decade to discover the first 10 or so quasars with redshifts of 7 or greater. Euclid has already found more than that in a single year, more than doubling the known population of these exceptionally ancient objects.
Machine learning has become just as important as new telescopes. Advanced algorithms can sift through tens of millions of astronomical sources and identify the handful of genuine quasars hidden among countless stars that appear nearly identical.
Hennawi’s group spent years developing the software behind these discoveries. He also leads development of PypeIt, the data processing software used by University of California astronomers working with the Keck telescopes. Thanks to the university’s privileged access to Keck, two-thirds of the newly discovered quasars, including the three most distant, were confirmed there.
The team’s next milestone is to discover the first quasar beyond a redshift of 8, which would reveal an object from within the universe’s first 630 million years.
The discoveries are only the beginning. Approved observing programs with the James Webb Space Telescope will measure the masses of these black holes, study the gas surrounding them, and use their light to trace how reionization unfolded. Meanwhile, the Atacama Large Millimeter Array will examine the dust, gas, and star formation inside their host galaxies.
“The bigger vision is to stitch all of this together into a coherent timeline,” Hennawi said: “a quasar chronicle of the first billion years.”
Reference: “Euclid: Discovery of 31 new quasars at 6.6 < z < 7.8” by D. Yang, J. F. Hennawi, F. Guarneri, J. Wolf, S. Belladitta, J.-T. Schindler, A. C. N. Hughes, E. Bañados, D. J. Mortlock, J. Yang, F. Wang, X. Fan, K. Jahnke, D. Stern, C. J. Willott, A. J. Barth, H. J. A. Rottgering, R. G. Varadaraj, R. Decarli, A.-C. Eilers, M. Ezziati, Y. Fu, J. Huang, X. Jin, Y. Kang, L. N. Martinez-Ramirez, Y. Matsuoka, M. Onoue, R. Pello, R. P. Remigio, W. L. Tee, B. Venemans, G. Vietri, B. Wang, L. J. Abbo, H. Atek, S. Bisogni, S. E. I. Bosman, R. A. A. Bowler, C. J. Conselice, F. B. Davies, C. M. Gutierrez, Y. Harikane, K. Rubinur, C. C. Lovell, M. Magliocchetti, J. Matthee, F. Ricci, M. Scialpi, D. Scott, L. Spinoglio, F. Tarsitano, Y. Toba, F. Walter, J. R. Weaver, G. Zamorani, B. Altieri, A. Amara, S. Andreon, H. Aussel, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, J.-C. Cuillandre, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, M. Douspis, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. Gwyn, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Jhabvala, S. Kermiche, B. Kubik, K. Kuijken, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, H. J. McCracken, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, J. J. Mohr, A. Mora, M. Moresco, L. Moscardini, E. Munari, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, G. D. Racca, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, H.-W. Rix, E. Romelli, M. Roncarelli, C. Rosset, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, M. Sauvage, M. Schirmer, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, G. Fabbian, M. Huertas-Company, J. Martín-Fleitas, P. Monaco, V. Scottez and M. Viel, 6 July 2026, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202658883
Daming Yang, Antoine Basset and Jean-Charles Cuillandre of the Euclid Consortium contributed to this story.
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