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Supermassive black holes, often millions of times heavier than the sun, are typically hidden at the centers of most galaxies, making them challenging to observe and study. Contrary to the common portrayal of black holes incessantly consuming matter, many of them experience extensive periods of inactivity.
This phenomenon was observed in the black hole located in SDSS1335+0728, a seemingly ordinary galaxy situated 300 million light-years away in the Virgo constellation. After decades of dormancy, this black hole has recently started emitting intense bursts of X-ray radiation.
The first indicators of renewed activity emerged in late 2019 when astronomers noted an unexpected increase in brightness in the galaxy. Following extensive observations, researchers determined that these changes likely signified the black hole’s transition into an active state. The central region of the galaxy is now recognized as an active galactic nucleus, informally referred to as “Ansky.”
“Upon detecting Ansky’s brightness in optical wavelengths, we immediately initiated further observations using NASA’s Swift X-ray space telescope and scrutinized prior data from the eROSITA X-ray telescope. However, at that point, we did not find any indications of X-ray emissions,” reported Paula Sánchez Sáez from the European Southern Observatory in Germany, who led the initial investigation into the black hole’s awakening.
Ansky’s Awakening
In February 2024, a research team directed by Lorena Hernández-García from Valparaiso University in Chile began observing X-ray bursts from Ansky occurring at nearly consistent intervals.
This research has been documented in the journal Nature Astronomy.
“This unique event presents an invaluable chance for astronomers to directly observe a black hole’s activity, utilizing X-ray telescopes such as XMM-Newton, along with NASA’s NICER, Chandra, and Swift. This phenomenon is categorized as a quasiperiodic eruption (QPE), which are fleeting flaring events. This marks the first instance we have witnessed such an eruption in a black hole actively re-emerging,” Hernández-García explained.
“The initial QPE was identified in 2019, and since then only a handful have been detected. The mechanisms behind them remain a mystery. Observing Ansky will enhance our understanding of black holes and their evolutionary processes,” she added.
“XMM-Newton has been essential for our research, being the sole X-ray telescope capable of detecting the faint background X-ray light occurring between the bursts. This capability allowed us to gauge Ansky’s brightness fluctuations, thereby calculating the energy it expels during these illuminating episodes,” noted Hernández-García.
Exploring Unusual Patterns
A black hole’s gravity can draw in surrounding matter, tearing it apart and forming a bright, hot, rapidly spinning accretion disk. Current theories suggest that QPEs may stem from interactions between such disks and external objects, which could range from small black holes to stars, potentially resulting in stellar destruction. However, there is no current evidence suggesting that Ansky has obliterated any stars.
Due to the distinctive nature of Ansky’s recurring X-ray bursts, researchers began to explore alternative explanations. They posited that the accretion disk might consist of gas captured from the surrounding environment instead of remnants of a disrupted star. In this context, the X-ray emissions could arise from energetic shocks in the disk, induced by a small celestial body moving through and disrupting the surrounding material.
“The X-ray emissions from Ansky are tenfold longer and more intense compared to typical QPEs,” noted Joheen Chakraborty, a team member and Ph.D. student at the Massachusetts Institute of Technology. “Each of these flare-ups releases an astonishing hundred times more energy than previously measured instances. Furthermore, Ansky displays the longest interval between eruptions ever detected, approximately 4.5 days. This phenomenon challenges our existing theoretical frameworks regarding the origins of these X-ray outbursts.”
Observing Dynamic Behavior
Monitoring Ansky’s real-time evolution offers astronomers an unparalleled chance to delve deeper into the dynamics of black holes and the explosive events they can generate.
“Currently, we find ourselves in a position where we possess more models than empirical data related to QPEs, necessitating enhanced observations for clarification,” stated Erwan Quintin, an ESA Research Fellow and X-ray astronomer.
“Initially, we believed that QPEs were a result of smaller celestial bodies being captured by larger black holes and spiraling inward. However, Ansky’s repeated outbursts suggest a more complex narrative. These recurring emissions may also be linked to gravitational waves that could be detected by ESA’s forthcoming LISA mission,” Quintin shared.
“The critical aspect of gathering these X-ray observations is to enrich the gravitational wave data and contribute to resolving the enigmatic behaviors of massive black holes,” he concluded.
Further Information: Discovery of extreme Quasi-Periodic Eruptions in a newly accreting massive black hole, Nature Astronomy (2025). DOI: 10.1038/s41550-025-02523-9
Source
phys.org