A groundbreaking discovery has finally unravelled a mystery surrounding black holes that has baffled astronomers for years. An international team of astrophysicists, led by Queen’s University Belfast, utilised Nasa’s Chandra X-ray Observatory and other advanced telescopes to make this significant breakthrough.
The discovery involves a massive black hole that ripped apart a star, and is now utilizing the stellar debris to collide with another star or smaller black hole. This new evidence has allowed astronomers to definitively connect two enigmatic phenomena that were previously only loosely related.
In 2019, astronomers observed a star getting too close to a black hole and being destroyed by its immense gravitational forces. After the star was shredded, its remnants formed a disc shape as they orbited the black hole, creating what scientists refer to as a “stellar graveyard”.
Over time, the disc has expanded outward and now intersects with a star, or potentially a stellar-mass black hole, orbiting the massive black hole at a safe distance. The orbiting star repeatedly passes through the debris disc approximately every 48 hours, resulting in breathtaking light displays and bursts of X-rays captured by Chandra.
Lead author Dr Matt Nicholl from Queen’s University Belfast likened the scenario to a diver creating a splash in a pool every time they enter the water. The collision between the orbiting star and the disc produces significant gas and X-ray emissions, creating a mesmerising spectacle each time the star swings around the black hole.
This discovery has shed light on the connection between tidal disruption events (TDEs) where objects are torn apart by black holes in a single burst of light, and the previously unexplained quasi-periodic eruptions (QPEs) emitting bright X-ray flashes from galactic centres.
Co-author Dr Dheeraj Pasham from the Massachusetts Institute of Technology expressed excitement about the breakthrough, stating, “It’s like getting a cosmic two-for-one in terms of solving mysteries.” The research involved combining data from multiple observations, with findings indicating that objects orbiting the black hole at intervals of about a week collide with the disc and trigger eruptions.
Dr Andrew Mummery from Oxford University highlighted the importance of this breakthrough in understanding the origins of these regular eruptions, noting that there is a delay before eruptions occur after a star is torn apart due to the time required for the disc to expand sufficiently.
This discovery carries implications for identifying more QPEs associated with tidal disruptions, which could provide insights into the prevalence and distances of objects in close orbits around supermassive black holes. This knowledge could be crucial for future gravitational wave observatories.
The Chandra programme is managed by Nasa’s Marshall Space Flight Centre, with science operations overseen by the Smithsonian Astrophysical Observatory’s Chandra X-ray Centre in Cambridge, Massachusetts. The team’s findings promise to deepen our understanding of the dynamic interactions surrounding black holes in the universe.