Astronomers have made a groundbreaking discovery: what may be the most massive black hole ever identified.

Located approximately five billion light-years away, this enormous black hole resides at the center of the galaxy SDSS J1148+1930 and has a mass equivalent to 36.3 billion suns.

To put this in perspective, the supermassive black hole at the heart of our own Milky Way galaxy weighs only 4.3 million solar masses. This newly discovered black hole is roughly 8,400 times more massive than that, highlighting its extraordinary size.

This discovery is so exceptional that scientists are now classifying it as 'ultra-massive' rather than the typical 'supermassive' designation, which is reserved for the most colossal black holes in the universe.

"This black hole is one of the top 10 most massive ever discovered and is likely the largest one," stated Thomas Collett, an astrophysicist at the University of Portsmouth. "While most previous measurements of black hole masses have been indirect and come with significant uncertainty, our new method has provided much more reliable data on this one."

Although theoretically, black holes can grow indefinitely, in practice, their growth is limited by the age of the universe. Since the universe is only 13.8 billion years old, even the most massive black hole could only reach around 50 billion solar masses before time runs out.

Detecting these ultra-massive black holes requires advanced techniques, one of which is known as gravitational lensing. In this process, the gravity of a galaxy acts as a natural magnifying glass, creating a unique visual pattern called the Cosmic Horseshoe. This consists of a curved arc of light surrounding a central blob that, when observed from Earth, forms a horseshoe-like shape.

The light from a distant source is magnified by the immense gravitational force of the black hole, producing a smear effect. It was during the study of such a cosmic horseshoe that scientists, led by Carlos Melo-Carneiro of the Federal University of Rio Grande do Sul in Brazil, uncovered this ultra-massive black hole.

"This black hole was found in a 'dormant' state, meaning it wasn't actively consuming material at the time of observation," Melo-Carneiro explained. "Its discovery was made possible solely due to its immense gravitational influence and the effect it had on its environment."

'This is amongst the top 10 most massive black holes ever discovered.' (Eugene Mymrin/Getty)

What makes SDSS J1148+1930 even more remarkable is that it is considered a 'fossil galaxy'—a single, massive galaxy that was once part of a larger cluster of separate galaxies. Over billions of years, these individual galaxies merged into one. Each of these original galaxies had its own supermassive black hole, and as the galaxies merged, so did their black holes, eventually forming this astonishing 36-billion-solar-mass giant.

This discovery could provide astronomers with crucial insights into the formation and growth of black holes, helping to unravel the mysteries of how they become so incredibly massive.