When a star ventures perilously close to a supermassive black hole, the intense gravitational forces tear it apart. The star’s outer layers stretch and elongate like taffy, with some material being drawn into the black hole while the rest is flung away. This cosmic drama offers a fascinating glimpse into the universe’s most extreme phenomena.
Yet, not all stars succumb immediately. Some manage to escape momentarily, only to return for subsequent encounters with the black hole. These rare, resilient stars provide valuable opportunities for scientists to explore the intricate dynamics of star destruction. One such star, known as AT2018fyk, has captured astronomers’ attention with its repeated returns to its black hole tormentor.
The AT2018fyk Event: A Cosmic Phenomenon
First detected in 2018 by the All-Sky Automated Survey for Supernovae (ASAS-SN), AT2018fyk appeared as a bright flare of light. This event was followed by observations from various space telescopes, including ultraviolet and X-ray emissions. The flare, originating from a distance of 800 million light-years, persisted for over a year before fading away. Remarkably, after a two-year lull, it reignited, signaling a new chapter in its cosmic journey.
The Rarity of Repeated Star Shredding
Black holes tearing apart stars are uncommon, occurring only once every 10,000 to 100,000 years in a given galaxy. Events like AT2018fyk, which exhibit repeated disruptions, are even more extraordinary. The rarity of such events enhances their scientific value, providing a unique window into the mechanics of stellar destruction.
Theoretical Insights from Dheeraj Pasham’s Study
In a study published in the August 20th edition of the Astrophysical Journal, Dheeraj Pasham from MIT and his team propose a compelling explanation for AT2018fyk’s behavior. They theorize that a massive star entered an elongated orbit around the black hole in 2018. This close encounter caused its outer layers to be stripped away, leading to the initial flare.
After the its first close pass, it entered a region of space largely devoid of stripped gas. When it approached the black hole again, about three years later, this empty zone resulted in diminished feeding and reduced brightness. The black hole continued to extract material, which eventually fell back into it after 1.5 to 2 years, reigniting the flare before a subsequent close passage extinguished it once more.
Future Observations and Predictions
Suvi Gezari from the Space Telescope Science Institute, who was not involved in the study, highlights the significance of these repeating tidal disruption events. They allow astronomers to track the star’s repeated orbits and gain insights into its physical characteristics and internal structure.
Currently, astronomers are monitoring the star for a distinctive feature: two tails of gas. One tail extends towards the black hole, while the other points away. During the black hole’s inactive phases, a faint X-ray glow from the escaping material might become observable. Instruments like the Neil Gehrels Swift Observatory, NICER, XMM-Newton, and the Chandra X-ray Observatory are on high alert for these emissions.
The study also anticipates that the next stellar interaction will occur in early 2025. Depending on the star’s nature, future encounters could lead to its complete disruption or a dramatic escape from the black hole’s grasp.
Conclusion
The repeated encounters of AT2018fyk with a supermassive black hole offer an unprecedented opportunity to study the complex physics of star-shredding events. As scientists continue to observe and analyze these interactions, they inch closer to unraveling the mysteries of cosmic forces and the fate of stars caught in the clutches of black holes.
