Euclid Finds Two Quasars Shining Like a Trillion Suns, Earliest Ever Seen

The European Space Agency's Euclid space telescope has found 31 very ancient quasars, among them two that are now the earliest ever observed, according to ScienceDaily, which republished the agency's announcement. Powered by supermassive black holes, both were already blazing with the light of a trillion Suns when the Universe was only 670 million years old.

The haul gives astronomers their first broad look at the kind of objects that lit up the young cosmos, rather than just the few brightest ones that earlier searches could detect.

The discovery by the numbers

31 quasars: the number of exceptionally ancient quasars Euclid has identified so far.
670 million years: the age of the Universe when the two record-setting quasars were already shining, about 5% of its present age.
A trillion Suns: the brightness those two objects radiated.
12 quasars: the number among the 31 with a redshift of 7 or greater, which places them within the Universe's first 770 million years.
7.77 and 7.69: the redshifts of the two record holders, EUCL J172902.75+641018.1 and EUCL J125308.55+705432.3. The previous record, set by an object found in 2021, was 7.64.
Just over 13 billion light-years: how far from Earth both record holders are.

What a quasar is and why these are hard to find

A quasar appears during a relatively short stretch of a galaxy's history, when huge amounts of gas and other material spiral toward the supermassive black hole at its center. The process releases so much energy that the galaxy's core can outshine everything else in the galaxy hundreds or even thousands of times over.

Astronomers have searched for the earliest quasars for decades because they carry clues about how the first galaxies and supermassive black holes formed. The hunt is difficult. Few galaxies had grown large enough to host such an object that early, the light reaching Earth is extremely faint, and the sources can be mistaken for much closer stars.

Why it matters: a first census of the early Universe's quasars

Until now, most known quasars from this era were exceptionally luminous ones that were simply easier to spot, which made it hard to understand the wider population. Euclid, launched in 2023, can scan huge areas of sky and pick up fainter objects, so it is turning up the dimmer examples as well.

The speed of progress is striking. According to the report, astronomers needed more than a decade to find roughly the first 10 quasars with a redshift of 7 or higher, and Euclid has passed that number in one year. Antonio La Marca, an ESA Research Fellow on the Euclid team, said the finding more than doubles the number of such ancient quasars known, and called it a first real census of quasars at the dawn of the Universe.

Daming Yang of Leiden University in the Netherlands, lead author of the discovery paper, said the quasars should help explain how such enormous systems formed and grew so quickly, which he described as one of the biggest mysteries in astrophysics.

A glimpse of a star-forming galaxy around one black hole

One of the new objects has already been studied in more detail. Silvia Belladitta and colleagues examined the second most ancient quasar in the group and found that it sits inside a galaxy full of gas and dust, where new stars are forming at a tremendous rate. That offers a rare view of the surroundings of an early supermassive black hole and could help researchers work out how the first massive galaxies grew alongside the black holes at their centers.

These quasars also date from the epoch of reionization, when the Universe emerged from a cold, dark state known as the dark ages. Increasingly energetic radiation heated the surrounding gas and ionized it, meaning it was split apart by energetic light, a transition that helped set the conditions that shaped the Universe.

Around Prague, based on reporting by ScienceDaily

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