The European Space Agency’s Euclid telescope has identified the most distant quasar ever observed, a blazing object designated EUCL J172902.75+641018.1 sitting at a redshift of approximately 7.77. That places it in a slice of cosmic history less than 670 million years after the Big Bang, surpassing the previous record holder, quasar J0313-1806, which was measured at redshift 7.642. The discovery is part of a larger haul of 31 newly confirmed quasars between redshifts 6.6 and 7.8, 12 of which date to the universe’s first 770 million years. Together, these objects sharpen a longstanding puzzle: how supermassive black holes grew so large so quickly in a young cosmos.
Why the oldest quasar sharpens the black-hole seed debate
Finding a quasar at redshift 7.77 is not simply a distance trophy. Each step deeper into the early universe tightens the clock on how much time a black hole had to accumulate mass. The two most distant objects in the new Euclid sample both emerged during the universe’s first few hundred million years, according to NASA’s summary of the findings. At those epochs, conventional models struggle to explain billion-solar-mass black holes if they started as the remnants of ordinary dead stars. Stellar-mass seeds would need to accrete matter at or above theoretical speed limits for hundreds of millions of years straight, a scenario most astrophysicists regard as implausible.
The alternative is direct collapse: massive gas clouds in the early universe bypassing normal star formation and instead falling straight into black holes weighing tens of thousands of solar masses from the start. These heavier seeds would need far less time to reach quasar-scale luminosities. The sheer number of high-redshift quasars Euclid has now cataloged provides a statistical test. If direct-collapse seeds are common, wide-field surveys should turn up more of these early quasars than stellar-remnant models predict. Comparing Euclid’s counts against forecasts from NASA’s upcoming Roman Space Telescope, which will scan overlapping redshift ranges with different depth and area tradeoffs, could distinguish between the two formation channels within the next few years.
Euclid’s wide field of view is central to this effort. Rather than staring deeply at a small patch of sky, the mission is designed to map a third of the celestial sphere with uniform image quality. That strategy makes it particularly effective at finding rare, bright objects such as high-redshift quasars. Once candidates are flagged photometrically, ground-based spectrographs can confirm their redshifts and reveal the broad emission lines that signify actively accreting supermassive black holes. As more of the survey area is processed, astronomers expect the tally of early quasars to grow, tightening constraints on how common massive seeds must have been.
Thirty-one quasars and a star-forming host galaxy at redshift 7.7
The discovery paper, posted as a preprint on arXiv, reports spectroscopic confirmation of all 31 objects. Twelve of those quasars sit at redshift 7 or above, corresponding to the first 770 million years of cosmic history. The record-breaking EUCL J172902.75+641018.1 at redshift 7.77 edges past J0313-1806, whose redshift of 7.642 was established by University of Arizona–led observations published in 2021.
A companion study published in Astronomy and Astrophysics focuses on a second high-redshift target, EUCL J125308.55+705432.3, pinning its systemic redshift at 7.6980 plus or minus 0.0004 using NOEMA millimeter-wave observations. That same paper, cataloged by IPAC at Caltech, reports a star-formation rate exceeding 250 solar masses per year in the quasar’s host galaxy. For context, the Milky Way forms roughly one to two solar masses of new stars per year. A rate above 250 solar masses per year at redshift 7.7 signals an extraordinarily active galaxy, one that was building stars at a furious pace while simultaneously feeding a central black hole.
ESA’s mission page lists both EUCL J172902.75+641018.1 at redshift 7.77 and EUCL J125308.55+705432.3 at redshift 7.69 as the two most ancient quasars in the sample. The previous record holder, J0313-1806, was measured at redshift 7.642 in a study that also used ALMA submillimeter data to characterize its host galaxy. Euclid’s new pair therefore pushes the frontier by a measurable margin, not a dramatic leap but enough to place fresh constraints on early black-hole growth and on the timing of galaxy assembly in the reionization era.
The broader sample of 31 quasars spans a range of luminosities and spectral properties. Some exhibit strong emission from ionized carbon and magnesium, while others show weaker lines, hinting at diversity in their accretion rates and surrounding gas. Because Euclid observes in the near-infrared, it can efficiently detect the redshifted ultraviolet light from these distant objects, including the sharp Lyman-alpha break that serves as a key redshift indicator. Follow-up spectroscopy then refines those estimates and separates true quasars from lower-redshift interlopers such as dusty galaxies.
Open questions Euclid’s quasar census cannot yet answer
Several gaps remain in the evidence. The discovery preprint provides spectroscopic confirmations and redshifts, but direct black-hole mass estimates for EUCL J172902.75+641018.1 have not appeared in the primary literature. Without a mass measurement, the most pressing question-whether this object’s black hole is heavier or lighter than expected for its age-stays open. The detailed host-galaxy data that exist for EUCL J125308.55+705432.3, including dust mass, far-infrared luminosity, and dynamical mass, have no published equivalent for the record holder.
Even for EUCL J125308.55+705432.3, key pieces of the puzzle are missing. The current observations constrain how rapidly the galaxy is forming stars and provide hints about the gas reservoir available for future growth, but they do not yet resolve the spatial structure of the star-forming regions or the precise geometry of the quasar’s immediate environment. High-resolution imaging from facilities such as the James Webb Space Telescope will be needed to disentangle the bright nucleus from its host and to map how star formation is distributed across the galaxy.
There are also broader uncertainties tied to the nature of preprint archives. The Euclid quasar results first appeared on arXiv’s open-access server, which allows rapid dissemination of research ahead of formal peer review. While this speeds up the flow of information and enables quick community feedback, it also means that some details-such as derived black-hole masses or refined error bars-may change between the preprint and the final journal publication. For now, astronomers treat the reported redshifts and object identifications as robust but remain cautious about over-interpreting secondary conclusions.
Ultimately, Euclid’s early quasar census is a starting point rather than a final answer. As the mission continues, deeper exposures and expanded sky coverage should reveal fainter and potentially even more distant quasars, filling in the bright end of the population at redshifts beyond 7. Combined with complementary surveys at X-ray, radio, and submillimeter wavelengths, these data will help determine whether the universe’s first supermassive black holes were born heavy through direct collapse or assembled more gradually from smaller seeds. For now, EUCL J172902.75+641018.1 stands as a new benchmark in that quest, a beacon from the cosmic dawn that both illuminates and complicates our picture of how the first giant black holes came to be.
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*This article was researched with the help of AI, with human editors creating the final content.
