Astronomers Discover Most Luminous Quasar Ever Observed

The black hole in the newly-discovered quasar SMSS J052915.80-435152.0 (hereafter called J0529-4351) accretes around one solar mass per day onto an existing mass of 17 billion solar masses.

In 1963, the Dutch-born American astronomer Maarten Schmidt identified the first quasar, known as 3C 273. It appeared as a remarkably bright star of 12th magnitude, and its redshift suggested that it was among the most distant objects known in the Universe at the time.

The two facts together implied an implausibly huge output of light and, ever since then, newly found quasars have impressed with their immense energy release from a small region of space.

This could only be explained as gravitational energy being converted into heat and light within a highly viscous accretion disk around a supermassive black hole.

Today, around a million quasars are known, although some specimens stand out from the crowd: in 2015, the ultra-luminous quasar J0100+2802 was identified with a supermassive black hole of 10 billion solar masses.

In 2018, an even more luminous object was found, J2157-3602, with a supermassive black hole of 24 billion solar masses.

Although their luminosity implies rapid growth, their existence is hard to explain: when black holes start from the remnant of a stellar collapse and grow episodically, they are not expected to reach the evident masses in the time from the Big Bang to the epoch of their observation.

The new record-breaking quasar is so far away from Earth that its light took over 12 billion years to reach us.

Called J0529-4351, the object was first detected using a 2.3-m telescope at the ANU Siding Spring Observatory.

Australian National University astronomer Christian Wolf and colleagues then turned to one of the largest telescopes in the world, ESO’s Very Large Telescope, to confirm the full nature of the black hole and measure its mass.

“We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe,” Dr. Wolf said.

The matter being pulled in toward this black hole, in the form of a disk, emits so much energy that J0529-4351 is over 500 trillion times more luminous than the Sun.

“All this light comes from a hot accretion disk that measures seven light-years in diameter — this must be the largest accretion disk in the Universe,” said Australian National University Ph.D. student Samuel Lai.

“It’s a surprise it remained undetected until now, given what we know about many other, less impressive black holes. It was hiding in plain sight,” said Dr. Christopher Onken, also from Australian National University.

The discovery is reported in a paper in the journal Nature Astronomy.

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C. Wolf et al. The accretion of a solar mass per day by a 17-billion solar mass black hole. Nat Astron, published online February 19, 2024; doi: 10.1038/s41550-024-02195-x