A quasar emits exceptional amounts of energy generated by matter falling into a supermassive black hole.Credit
NASA, ESA, Joseph Olmsted (STScI)
An international team of scientists has discovered 31 of the most ancient quasars ever found, including two that shatter previous records to become the earliest observed objects of their kind in cosmic history
Published in the journal Astronomy & Astrophysics, the study leverages data from the European Space Agency’s (ESA) Euclid space telescope to peer back to an era when the universe was in its absolute infancy.
The two record-breaking quasars emerged when the universe was a mere 670 million years old—less than 5% of its current age. Despite the youth of the cosmos at that time, these primordial beacons radiated the light of a trillion suns, fueled by central “monsters” weighing hundreds of millions to billions of times the mass of our sun.
The challenge of hunting the first beacons: Primordial quasars
Quasars are the hyper-luminous centers of distant galaxies, powered by supermassive black holes furiously devouring surrounding matter. Because they emit exceptional amounts of energy, they serve as cosmic lighthouses visible across billions of light-years.
However, hunting for quasars from the universe’s first 770 million years has historically been a nearly impossible task for ground-based observatories due to two main hurdles:
The imposter problem:
At such extreme distances, primordial quasars appear incredibly faint. In standard imaging surveys, they look virtually identical to thousands of much closer, ordinary stars within our own Milky Way galaxy.
Atmospheric infrared glow:
Due to the ongoing expansion of spacetime, the light from these ancient objects has been dramatically stretched from ultraviolet into near-infrared wavelengths (a phenomenon known as cosmological redshift). At these longer wavelengths, Earth’s atmosphere glows brightly, completely drowning out faint signals from deep space.
Euclid: The orbital game-changer
To bypass Earth’s infrared haze, astronomers turned to the Euclid space telescope, launched in 2023. Operating above the atmosphere, the Euclid Wide Survey can capture massive swathes of the sky—ultimately covering more than one-third of the total sky—at depths never before achieved from orbit.
The strategy has paid off exponentially. While it took astronomers more than a decade to find the first ten quasars at or above a redshift of 7, Euclid discovered 14 of them in a single year. In total, the telescope’s wide-field capabilities netted 31 new ancient quasars, more than doubling the world’s catalog of these elusive objects.
The two oldest specimens in the batch register unprecedented redshifts of 7.69 and 7.77, placing them just over 13 billion light-years away.
Algorithmic sifting and ground verification
Sifting through the mountain of data generated by Euclid required advanced computational tools. Co-author Joseph Hennawi, a physics professor at UC Santa Barbara, led the development of specialized machine-learning algorithms designed to filter through tens of millions of celestial sources and accurately distinguish true ancient quasars from stellar imposters.
Once candidate quasars were flagged by AI, the team utilized the twin Keck telescopes in Hawaii to confirm their distances and ages. Hennawi’s group used their custom data-processing software, PypeIt, to analyze the Keck spectroscopic data, verifying two-thirds of the new discoveries.
Chronicling the first billion years
The discovery of these ancient bodies challenges current cosmological models, as scientists do not yet have a definitive explanation for how supermassive black holes could have accumulated so much mass so quickly after the Big Bang.
Detailed analysis of the second-oldest quasar in the batch shows that it is embedded in a dense, dusty galaxy undergoing a furious burst of star formation. This environment provides crucial clues about the Epoch of Reionization—the pivotal era when the first stars and galaxies ionized the dark, neutral hydrogen fog filling the early cosmos.
The international team is already preparing follow-up observation programs. They will use the James Webb Space Telescope (JWST) to precisely calculate the masses of these early black holes and trace the progression of cosmic reionization. Concurrently, the Atacama Large Millimeter Array (ALMA) in Chile will target the glowing cosmic dust within the host galaxies to map out their star-formation rates, stitching the data together into a comprehensive timeline of the universe’s first billion years.