51³Ô¹ÏÍø

The European Space Agency’s Euclid space telescope has discovered 31 of the most distant known quasars dating back to the earliest chapters in cosmic history, including the two most ancient quasars ever observed.

Among the newly discovered objects are two record-breaking quasars that were already shining when the Universe was just 670 million years old, a mere 5% of its current age. The full sample of 31 quasars, however, spans a narrow range of early cosmic history dating from roughly 700 to 800 million years after the Big Bang.

Each is powered by a supermassive black hole around a billion times the mass of the Sun, surrounded by swirling discs of superheated material whose intense radiation allows them to comfortably outshine entire galaxies.

Researchers at 51³Ô¹ÏÍø are among those contributing to the mission. Professor Daniel Mortlock, from 51³Ô¹ÏÍø’s Departments of Physics and Mathematics, has acted as one of two co-leads of the Quasar Work Package in the Primeval Universe Science Working Group since 2014 and has spent over a decade preparing for this moment.

Professor Mortlock said, “It is fabulous to see all this planning and hard work come to fruition with these discoveries of some of the most extreme astronomical objects in the early Universe.”

These findings were published on the this morning.

Finding needles in a cosmic haystack

Quasars mark a brief but dramatic stage in a galaxy’s lifetime, when matter falling into the central supermassive black hole releases enormous amounts of energy. Their extreme brightness makes them powerful probes of the early Universe, offering rare insights into how the first galaxies and black holes formed and grew.

Ironically, given their brightness, these first quasars are exceptionally difficult to find. They are extremely rare, and their primordial light is faint by the time it reaches Earth and can easily be mistaken for that of a nearby star. This has made it challenging to identify quasars from the earliest stages of the Universe.

Until now, astronomers had identified only a handful of quasars from this period, the brightest outliers in a much larger, mostly hidden population. Euclid has begun to change this, allowing scientists to move beyond isolated discoveries towards something closer to a true population study.

Euclid’s first glimpse of the early quasar population

Launched in July 2023, the Euclid satellite is enabling a new approach to the search for ancient quasars by surveying vast areas of the sky in infrared light from space. This allows the mission to detect the faint glow of extremely distant objects with far greater efficiency than has previously been possible.

The challenge of finding the small number of distant quasars in a huge dataset like that from Euclid is the ultimate ‘needle in a haystack’ problem.  But while such a ‘big data’ challenge is very modern, it turns out the best solution is to use an approach which has been known for centuries: Bayes’s theorem Professor Daniel Mortlock Professor of Astrophysics and Statistics Department of Physics

The discovery of these 31 new quasars represents Euclid’s first major sample of very distant examples. Two of these set new records as the most ancient quasars ever observed, pushing observations deeper into cosmic history than ever before.

Discovering even a small number  at this distance previously required years of effort. Remarkably, Euclid has already delivered the largest sample of these distant quasars to date within its first year’s worth of data.

Professor Mortlock helped coordinate efforts to develop methods needed to systematically sift through vast datasets, narrowing down hundreds of millions of detected objects to a small number of promising candidates.  

Professor Mortlock explained, “The challenge of finding the small number of distant quasars in a huge dataset like that from Euclid is the ultimate ‘needle in a haystack’ problem.  But while such a ‘big data’ challenge is very modern, it turns out the best solution is to use an approach which has been known for centuries: Bayes’s theorem.”

These ancient quasars offer a new window onto the epoch of reionisation, a pivotal period when the first luminous sources transformed the early Universe from a cold, dark state into the ionised cosmos seen today.

By studying early quasars as a population, researchers hope to better understand how supermassive black holes formed so rapidly and how they influenced the galaxies around them.

The discoveries were made using early data from Euclid’s Wide Survey, which will eventually cover more than one-third of the entire sky and observe billions of galaxies. As the mission continues, astronomers expect Euclid to complete what would be the fullest ever census of these extraordinary objects.