Brightest and fastest growing: Astronomers identify record-breaking quasar

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have characterized a bright quasar, finding that it is not only the brightest of its type, but also the the brightest object ever observed. Quasars are the bright cores of distant galaxies and are powered by supermassive black holes.

The black hole in this record-breaking quasar is growing in mass by the equivalent of a sun per day, making it the fastest-growing black hole to date.

The black holes that power quasars collect matter from their surroundings in an energetic process that emits large amounts of light. So much so that quasars are among the brightest objects in our sky, meaning that even the most distant ones are visible from Earth. Generally, the brightest quasars indicate the fastest growing supermassive black holes.

“We have discovered the fastest growing black hole known to date. It has a mass of 17 billion suns and consumes just over one sun per day. This makes it the most luminous object in known universe,” says astronomer Christian Wolf. at the Australian National University (ANU) and lead author of the published study Natural astronomy. The quasar, called J0529-4351, is so far from Earth that its light took more than 12 billion years to reach us.

The matter attracted to this black hole, in the form of a disk, emits so much energy that J0529-4351 is more than 500,000 billion times brighter than the sun. “All this light comes from a hot accretion disk that is seven light years across. It must be the largest accretion disk in the universe,” explains the ANU Ph.D. student and co-author Samuel Lai. Seven light years is about 15,000 times the distance from the sun to Neptune’s orbit.

Remarkably, this record quasar was hiding in plain sight. “It is surprising that it has remained unknown until today when we already know about a million less impressive quasars. It has been staring us in the face until now,” says co-author Christopher Onken, an astronomer. at the ANU. He added that this object appeared in images from the ESO Schmidt Southern Sky Survey from 1980, but was not recognized as a quasar until decades later.

Searching for quasars requires precise observational data from large areas of the sky. The resulting data sets are so large that researchers often use machine learning models to analyze them and distinguish quasars from other celestial objects.

However, these models are trained on existing data, which limits potential candidates to objects similar to those already known. If a new quasar is brighter than any previously observed, the program could reject it and instead classify it as a star not too far from Earth.

An automated analysis of data from the European Space Agency’s Gaia satellite flew past J0529-4351 because it was too bright to be a quasar, suggesting it was a star instead. Researchers identified it as a distant quasar last year using observations from the 2.3-meter ANU telescope at the Siding Spring Observatory in Australia.

However, discovering that it was the most luminous quasar ever observed required a larger telescope and measurements from a more precise instrument. ESO’s VLT X-shooter spectrograph in the Chilean Atacama Desert provided crucial data.

The fastest growing black hole ever observed will also be a perfect target for the GRAVITY+ upgrade of ESO’s VLT Interferometer (VLTI), designed to precisely measure the mass of black holes, including those distant from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-meter telescope under construction in the Chilean Atacama Desert, will make the identification and characterization of these elusive objects even more feasible.

The discovery and study of distant supermassive black holes could shed light on some of the mysteries of the early universe, including how they and their host galaxies formed and evolved. But that’s not the only reason Wolf is looking for them. “Personally, I just like the chase,” he says. “A few minutes a day I feel like a kid again, playing treasure hunt, and now I’m putting everything I’ve learned since then on the table.”