Astronomers see, for the first time, the awakening of a massive black hole in real time

A team of astronomers are witnessing changes never before seen in a galaxy, probably the result of the sudden awakening of the black hole massive in its core, according to a study published this Tuesday in the journal Astronomy & Astrophysics and carried out with the long-range telescope (VLT) of the European Southern Observatory (ESO).

At the end of 2019, the previously unremarkable galaxy SDSS1335+0728 suddenly began to shine brighter than ever.

“Imagine that you have been observing a distant galaxy for years and it always seems calm and inactive and suddenly its core begins to show drastic changes in brightness in a totally different way than what had been observed before.“, declares Paula Sánchez Sáez, astronomer at the ESO in Germany and lead author of the study.

To understand why, the team has used archival data and new observations from several space and ground-based observatories to study how the galaxy’s brightness has varied.

By comparing data taken before and after December 2019 they found that SDSS1335+0728 now radiates much more light in ultraviolet, optical and infrared wavelengths. The galaxy also began emitting X-rays in February 2024.

“The most tangible option to explain this phenomenon is that we are seeing how the nucleus of the galaxy is beginning to show activity“, declares co-author Lorena Hernández García, from the Millennium Institute of Astrophysics (MAS) and the University of Valparaíso, in Chile.

For this striking brightness increase, Chilean broker Machine Learning for Rapid Classification of Events (ALeRCE) classified SDSS1335+0728 as a “active galactic nucleus” (AGN), which is a compact, bright region fed by a massive black hole.

Although previous studies indicated that inactive galaxies become active after several years, this is the first time that the process itself, the awakening of the black hole, has been observed in real time.

“This behavior is unprecedented”says Sánchez Sáez, who is also affiliated with the Millennium Institute of Astrophysics (MAS) in Chile

Currently, more than four years after his “switched on”, the galaxy, SDSS1335+0728, continues to increase in brightness, leading astrologers to rule out other phenomena, such as supernova explosions or tidal disruption events (when a star gets too close to a black hole and collapses). tears) that also make galaxies shine suddenly but for a maximum period of a few hundred days.

Furthermore, the variations detected in the galaxy, which is located 300 million light-years away in the constellation Virgo, are unlike anything that has been observed before, leading to the possibility that a unusually slow tidal disruption event or even a new phenomenon.

“Regardless of the nature of the variations, this galaxy provides valuable information about how black holes grow and evolve”, concludes the main author of the study.