In a cosmic first, astronomers have observed a supermassive black hole spring to life after more than two decades of silence a groundbreaking event that could reshape how we understand galaxy evolution and black hole growth.
The galaxy, known as SDSS1335+0728, lies around 300 million light-years away in the constellation Virgo. It had shown no signs of activity for years until late 2019, when astronomers noticed something startling. The galaxy’s core began glowing intensely, first in ultraviolet, optical, and infrared light, and then in February 2024, it started emitting X-rays all signs of a newly awakened black hole.
This awakening, captured in real time, marks the first time scientists have directly observed a supermassive black hole transition from a dormant to an active state. The galaxy’s central black hole, estimated to be about one million times the mass of our Sun, appears to be feeding on surrounding gas a process that has turned SDSS1335+0728 into what is known as an active galactic nucleus (AGN).
“Imagine watching a galaxy for years and seeing nothing change and then suddenly, its core flares up with an intensity we’ve never seen before,” said Paula Sánchez Sáez, an astronomer at the European Southern Observatory (ESO) and lead author of the study accepted for publication in Astronomy & Astrophysics.
The discovery was made using data from several observatories, including the ESO’s Very Large Telescope and the Zwicky Transient Facility. What sets this event apart from typical black hole flares is its persistence. Normally, if a star wanders too close to a black hole and gets shredded in a tidal disruption event, the resulting light show fades in a matter of months. But in this case, the brightness has lasted for years, hinting at a new kind of cosmic behavior.
Co-author Claudio Ricci described it as witnessing a “giant monster” come alive. “Black holes of this size usually stay hidden and quiet. This one gave us a rare look into its awakening and it’s not done yet.”
The implications are far-reaching. This unexpected transformation could help scientists refine existing models of black hole accretion, offering insights into how black holes grow and influence star formation in their host galaxies.
Researchers are now turning to powerful instruments like MUSE on the Very Large Telescope and the upcoming Extremely Large Telescope to gather more data. They hope to determine whether this is a slow-burning tidal event or an entirely new class of outburst.
“Whatever is behind this sudden brightness, it’s teaching us something new about how black holes behave,” Sánchez Sáez said. “We may be witnessing just the beginning of many more such awakenings across the universe.”
The galaxy SDSS1335+0728 may have been quiet for 20 years but its story is just beginning.