ESO/M. Kornmesser
An artist's impression depicts a quasar that has been discovered to be the brightest object in the universe, and it's powered by the fastest-growing black hole ever observed.

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Astronomers have spotted the brightest known object in the universe, and it’s a quasar powered by the fastest-growing black hole on record, according to a new study. Initially classified as a star, the quasar managed to hide in plain sight until recently, surprising scientists.

Quasars are the luminous cores of distant, ancient galaxies. These gleaming phenomena are without a doubt the most dazzling objects in the cosmos — and scientists believe they are fueled by supermassive black holes that are the central engines of large galaxies.

When astronomers spied a quasar called J0529-4351 using the European Southern Observatory’s Very Large Telescope, they discovered that the incredibly distant object is so far from our solar system that its light has taken more than 12 billion years to reach Earth.

The black hole powering the quasar devours the equivalent of one sun per day and has a mass about 17 billion times that of our sun, the researchers found. A study detailing the awe-inspiring discovery appeared Monday in the journal Nature Astronomy.

“The incredible rate of growth also means a huge release of light and heat,” said lead study author Christian Wolf, associate professor in the Australian National University’s College of Science, in a statement. “So, this is also the most luminous known object in the universe. It’s 500 trillion times brighter than our sun.”

Astronomers are eager to study the quasar, as well as other elusive objects, with new instruments and observatories in the future because distant supermassive black holes could answer key questions about the early days of the universe, such as how galaxies formed and evolved.

A black hole is massive power source

The intense gravitational influence of black holes draws matter toward these celestial objects in such an energetic way that the process creates light. The blinding radiation is due to the black hole’s accretion disk, or the ring around the black hole where material gathers before being consumed.

“It looks like a gigantic and magnetic storm cell with temperatures of 10,000 degrees Celsius (18,032 degrees Fahrenheit), lightning everywhere and winds blowing so fast they would go around Earth in a second,” Wolf said.

Astronomers know that if they spot an incredibly luminous quasar, it means a rapidly growing supermassive black hole also is present, and J0529-4351 is the most impressive yet on both counts.

“All this light comes from a hot accretion disc that measures seven light-years in diameter — this must be the largest accretion disc in the Universe,” said study coauthor Samuel Lai, a doctoral student at the Australian National University’s Research School of Astronomy & Astrophysics, in a statement.

Hiding in plain sight

Wolf said he isn’t sure that the records set by J0529-4351 can ever be broken. Although another team of scientists reported that the Hubble Space Telescope spotted a quasar as bright as 600 trillion suns in 2019, the object’s luminosity was intensified by gravitational lensing, a phenomenon in which galaxy clusters help to magnify objects in the distant universe. The true luminosity of the quasar, called J043947.08+163415.7, is thought to be closer to about 11 trillion suns, according to the researchers who made the initial discovery.

The quasar first appeared in images from the European Southern Observatory’s Schmidt Southern Sky Survey in 1980, but it wasn’t recognized as a quasar.

“It is a surprise that it has remained unknown until today, when we already know about a million less impressive quasars. It has literally been staring us in the face until now,” said study coauthor Dr. Christopher Onken, research fellow at the Australian National University’s Research School of Astronomy & Astrophysics, in a statement.

Searching for quasars is an imperfect science

Hunting for clues in large sky surveys is the best way to find distant quasars, but the giant datasets generated by these massive surveys often must be fed into machine-learning models for analysis. The computer models can only pick out quasar candidates that appear similar to known objects because the software is trained on existing data.

Digitized Sky Survey 2/Dark Energy Survey/ESO
An image of the quasar's location was created using data from the Digitized Sky Survey 2, while the inset was provided by the Dark Energy Survey.

Newly discovered quasars may be more luminous than those observed in the past, which means computer models could reject the objects by classifying them as bright nearby stars.

This misidentification is what happened to J0529-4351 at first when an automated program analyzing data from the European Space Agency’s Gaia satellite categorized the object as a star in June 2022.

But astronomers determined that the object was a quasar when they observed it in 2023 while using the 2.3-meter telescope at the Australian National University’s Siding Spring Observatory near Coonabarabran in New South Wales. The team followed up with observations from the powerful Very Large Telescope in Chile’s Atacama Desert to confirm details about the black hole, including its hefty mass.

“Personally, I simply like the chase,” Wolf said. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.”