Black Hole Devours Star & Continues to Emit Radio Waves for 6 Years
- Astronomers are observing an exceptionally energetic and persistent radio signal emanating from a supermassive black hole that shredded a star in 2018.
- These events, known as tidal disruption events, occur when a star ventures too close to a supermassive black hole and is torn apart by its immense gravitational forces.
- “This is really unusual,” said Yvette Cendes, an astrophysicist at the University of Oregon and lead author of a new study published in The Astrophysical Journal.
A Black Hole’s Unusual Afterglow Challenges Astrophysical Models
Astronomers are observing an exceptionally energetic and persistent radio signal emanating from a supermassive black hole that shredded a star in . The object, designated AT2018hyz, continues to brighten in radio wavelengths years after the initial disruption, defying expectations about the aftermath of such cosmic events. The ongoing emission is now roughly 50 times brighter than when first detected and is predicted to peak around .
These events, known as tidal disruption events, occur when a star ventures too close to a supermassive black hole and is torn apart by its immense gravitational forces. This process, often described as “spaghettification,” stretches the star into elongated streams of gas. Typically, the resulting emission from the swirling debris disk around the black hole peaks relatively quickly and fades within months. AT2018hyz, however, has exhibited a remarkably different behavior.
“This is really unusual,” said Yvette Cendes, an astrophysicist at the University of Oregon and lead author of a new study published in The Astrophysical Journal. “I’d be hard-pressed to think of anything rising like this over such a long period of time.”
Cosmic Indigestion and a Persistent Radio Jet
The black hole, located approximately 665 million light-years from Earth, has a mass roughly five million times that of our Sun – comparable to the supermassive black hole at the center of our own Milky Way galaxy. The unfortunate star consumed was a red dwarf, with a mass about one-tenth that of the Sun.
Initially, AT2018hyz didn’t stand out from other tidal disruption events when first observed in using optical telescopes. However, subsequent radio observations revealed the unusual and intensifying signal. The delay in detecting the radio emission – appearing years after the initial optical detection – is a key aspect of what makes this event so intriguing.
The current emission isn’t a typical afterglow. Instead, it’s a powerful jet of material ejected from the black hole, intensifying over years. This sustained and increasing energy output is what sets AT2018hyz apart. The energy being released rivals that of a gamma-ray burst, potentially making it one of the most powerful single events ever detected in the universe.
Understanding the Mechanism Behind the Prolonged Emission
While tidal disruption events are relatively common, the prolonged and intensifying radio emission from AT2018hyz presents a puzzle for astrophysicists. The standard model predicts a rapid decline in brightness as the debris disk dissipates. The fact that this system continues to brighten suggests that a different mechanism is at play.
Researchers believe the sustained emission is linked to the way the black hole is interacting with the remaining stellar debris. The material isn’t simply falling into the black hole; instead, it’s being channeled into a powerful, focused jet. The exact process driving this jet and its continued intensification remains an area of active research.
Cendes explained that the black hole is exhibiting a case of “cosmic indigestion,” continuing to “burp out” the remains of the shredded star for an extended period. The team is now focused on understanding why this particular black hole is behaving so differently from others observed during similar events.
Implications for Black Hole Physics
The study of AT2018hyz offers a unique opportunity to probe the physics of supermassive black holes and their interactions with surrounding matter. The prolonged radio emission provides a window into the processes occurring near the event horizon – the point of no return beyond which nothing, not even light, can escape.
The observation also challenges existing models of tidal disruption events, suggesting that these events may be more diverse and complex than previously thought. The team’s prediction of a peak in radio emission around will allow for continued monitoring and further insights into the evolution of this unusual system.
“This event is a reminder that there’s still much we don’t understand about black holes and their behavior,” Cendes said. “It highlights the importance of continued observations and theoretical modeling to unravel the mysteries of these fascinating objects.”