Euclid's discovery of a new population of ancient quasars

2026-07-12T09:39:31Z

The European Space Agency’s Euclid mission has found 31 previously unknown quasars at redshifts between 6.6 and 7.8. Twelve lie beyond redshift 7, more than doubling the number known in that range before Euclid. The most distant, EUCL J172902.75+641018.1, has a redshift of about 7.77 and is currently the most distant quasar reported. [1] [2]

Why an early quasar is difficult to explain

A quasar is not a star. It is the extraordinarily bright centre of a galaxy where matter falling toward a supermassive black hole forms a hot accretion disk. Some of the new objects shine with the light of roughly a trillion Suns even though they are observed only about 670 million years after the Big Bang. [3]

That timing creates the scientific problem. A black hole must begin from a seed, acquire matter and grow, but radiation and feedback from the accretion process can limit how rapidly it feeds. Finding very massive, luminous systems so early tests models of the first black-hole seeds, galaxy formation and the availability of dense gas.

From rare records to a population

The discovery came from roughly 3,000 square degrees observed during the first 18 months of Euclid’s wide survey. Researchers used probabilistic and machine-learning selection on Euclid imaging, added other optical data where available and then performed spectroscopic follow-up on 123 candidates. Thirty-one were confirmed as high-redshift quasars. [2]

The value is therefore larger than another distance record. A sample allows astronomers to estimate how common early quasars were, compare their luminosities and environments, and test whether the brightest objects are unusual survivors or evidence of a broader growth mechanism. [1] [3]

Euclid’s next contribution will come from scale: as the survey expands, the distribution of these quasars should constrain how the first giant black holes and their host galaxies emerged during the Universe’s transition out of its cosmic dark age.

References

Euclid discovers the most ancient quasar in the Universe

Euclid: Discovery of 31 new quasars at 6.6 < z < 7.8

Scientists have discovered the oldest quasar ever seen