A supermassive black hole located in the center of the SDSS1335+0728 galaxy, about 300 million light years from the earth, recently manifested An unexpected activity, releasing intense and regular flashes of X -ray that immediately captured the attention of the international astrophysical community. After a prolonged retirement period, This gravitational giant suddenly “awakened”, giving rise to a rare phenomenon which offers an extraordinary opportunity to study the behavior of a black hole in real time. The observation of these energetic events, made possible thanks to the abilities of the XMM-Newton space telescope of the European Space Agency (ESA), has led to unpublished discoveries on the dynamics of supermassicci black holes. The results of this researchconducted by an international team of scientists who also includes researchers from the National Institute of Astrophysics (INAF), they were published on the prestigious magazine Nature Astronomy.
Although the supermaxicci black holes, with masses that can exceed millions or even billions of times that of our sun, are considered to be hidden at the center of most of the galaxies, their intrinsic nature makes them difficult to identify and, consequently, to be studied. Contrary to the common idea of cosmic “devourers” in continuous activity, these celestial objects can spend extremely long periods in a dormant phase. This was the case of the black hole in the center of SDSS1335+0728, affectionately Nicknamed Ansky, remaining inactive for decades. However, in 2019, The astronomers recorded a sudden “ignition” of the guest galaxy, followed by the emission of extraordinary flashes of X -rays. These unequivocal signals led to the conclusion that Ansky had entered a new active phase, transforming the galaxy that hosts it into an active galactic nucleus.
In February 2024, a research team led by Lorena Hernández-García, astronoma at the University of Valparaiso in Chile, began to monitor the regular flashes of X rays from ANSKY. “This rare event offers us the unique possibility of observing the behavior of a black hole in real time, exploiting the potential of XMM-Newton spatial telescopes and those of NASA Nicer, Chandra and Swift “, The researcher explains. “This phenomenon is known as almost periodic eruption (almostperiodic Eruption, QPE) short -lived and it is the first time that we observe a similar event in a black hole that seems to have just woke up“.
Phenomena of this type had previously been associated with small stars or other objects that interact with the subject present in the growth disc which orbits around the black hole. However, in the case of Ansky, there have been no evidence of a star in the destruction phase. Astronomes advance the hypothesis that flashes can originate from lower mass objects that repeatedly disturbed the material of the growth disc, generating powerful shock waves that release enormous quantities of energy. Each of these eruptions releases an energy a hundred times higher than the typical almost periodic eruptions: they are also ten times longer and bright, and manifest themselves with an unprecedented cadence of about 4.5 days, putting a strain on the theoretical models existing on black holes.
At present, the theoretical models on almost periodic eruptions far exceed the amount of observational data available, making further observations necessary to fully understand the nature of this fascinating phenomenon.
“Despite the considerable activity detected in the X -ray band, Ansky still appears in a state of quiescence in the radio band“, he comments Gabriele Bruni, Inf researcher and co-author of the publication. “In fact, neither our observations conducted with the Australian RadioTelescope Atca, nor the radio observational campaigns that have monitored its region of sky in recent years have detected emissions from its direction, thus excluding the presence of a relativistic jet generated during the reactivation of the black hole. In the coming months we will continue to carefully monitor Ansky to identify the potential birth of a jet, a phenomenon already observed in other cases of active galactic nuclei that have undergone reactivation“.
Ansky’s repetitive eruptions could also be associated with the generation of gravitational wavesa primary objective of the future Lisa of ASA mission. The joint analysis of the data collected in the Band of X -rays and studies on gravitational waves will help reveal the mystery of how massive black holes evolve and interact with the surrounding cosmic environment.