The discoveries include the two most distant quasars ever observed, dating back to just 670 million years after the Big Bang, when the Universe was only around 5% of its current age.
The findings significantly expand the known population of ancient quasars, more than doubling the number identified at this early stage of cosmic history.
By uncovering these distant objects, researchers have gained new opportunities to investigate how the first supermassive black holes and galaxies formed and evolved.
Discovered through data from Euclid’s Wide Survey, the newly identified quasars demonstrate the telescope’s ability to detect faint and extremely distant objects across vast areas of the sky.
Scientists believe the results mark a major advance in understanding one of the most important periods in the evolution of the cosmos.
Understanding ancient quasars
Quasars are among the brightest objects in the Universe. They form during a short-lived phase in a galaxy’s evolution when enormous quantities of gas and dust fall into its central supermassive black hole.
As this material is consumed, vast amounts of energy are released, causing the galaxy’s core to outshine the rest of the galaxy by hundreds or even thousands of times.
Because they are so luminous, quasars act as cosmic beacons that allow astronomers to study conditions in the distant Universe. However, the earliest examples are exceptionally difficult to detect.
Only a small number of galaxies had grown large enough to host supermassive black holes at that time, and the light from these ancient objects is both faint and easily mistaken for nearer stars.
For decades, researchers have searched for these rare objects to better understand how massive black holes grew so rapidly in the Universe’s infancy.
Euclid expands the cosmic census
Since its launch in 2023, the Euclid telescope has begun transforming that search.
The mission has now discovered 31 previously unknown ancient quasars, including 12 with redshifts of 7 or higher, representing a period within the first 770 million years after the Big Bang.
This dramatically increases the available sample for scientific study, allowing astronomers to investigate the broader population rather than focusing only on the brightest and rarest examples.
The two most distant discoveries, designated EUCL J172902.75+641018.1 and EUCL J125308.55+705432.3, have redshifts of 7.77 and 7.69 respectively. Located more than 13 billion light-years from Earth, they are now the earliest known quasars ever identified.
Researchers say the discoveries more than double the known population of quasars from this period of cosmic history. Previous surveys required more than a decade to identify around ten quasars at comparable distances, while Euclid has surpassed that figure in roughly a year of observations.
Insights into the first galaxies
Follow-up observations of one of the newly discovered quasars have already provided valuable clues about the environment surrounding these early black holes.
Astronomers found that the quasar resides within a galaxy rich in gas and dust that is undergoing intense star formation. The observation offers a rare glimpse of what the host galaxies of the earliest supermassive black holes may have looked like during the Universe’s formative years.
The discoveries also shed light on the epoch of reionisation, a pivotal chapter in cosmic history when the Universe transitioned from the so-called “dark ages” into a state filled with ionised gas after the first stars and galaxies began emitting energetic radiation.
Understanding this period is critical because it laid the foundations for the large-scale cosmic structures observed today.
A powerful mission for the dark Universe
The discoveries highlight the unique capabilities of the Euclid telescope, which combines wide-area sky coverage with high-resolution imaging and infrared observations from space. This combination enables scientists to identify extremely distant objects far more efficiently than previous surveys.
The discoveries were made using data from the Euclid Wide Survey, which will eventually map more than one-third of the entire sky.
Alongside its search for ancient quasars, the mission is designed to investigate dark matter and dark energy by observing billions of galaxies and tracing the large-scale structure of the Universe.
As the survey continues, astronomers expect Euclid to uncover many more distant quasars, creating the most comprehensive catalogue yet of these extraordinary objects and providing new insights into how the earliest galaxies and supermassive black holes emerged shortly after the birth of the Universe.
