An international team of astronomers, including researchers from our Department of Physics, has observed a seemingly dormant supermassive black hole reawaken.
Supermassive black hole reawakening
In less than three years, the black hole at the centre of galaxy ESO 511-G030 became more than ten times brighter in ultraviolet and X-ray light.
The discovery challenges existing models of how quickly these changes can happen. It also offers a rare view of how supermassive black holes switch between active and inactive states.
Six years of watching
The study used NASA's Neil Gehrels Swift Observatory to monitor the galaxy for six years, capturing the black hole's behaviour in remarkable detail.
For the first time, researchers followed the almost complete reactivation of the black hole's accretion disc in real-time.
An accretion disc is a swirling structure of hot gas that surrounds a black hole. As it falls inward, it releases vast amounts of energy.
The data showed that the black hole spent around three years in a low-activity state before beginning to recover in 2021.
By 2023, it has regained most of its original brightness.
The findings suggest that supermassive black holes much like their smaller cousins, stellar-mass black holes, where similar state changes have previously been seen.
The transition occurred when the accretion rate was about 1% of the maximum theoretically sustainable value.
Astronomers have seen the same threshold in smaller black hole systems - suggesting a common physical mechanism, operating across black holes of vastly different sizes.
Outpacing existing models
The rate of change observed in this study challenges the existing models of supermassive black hole accretion rates - outpacing their projected change timescales significantly.
Professor Chris Done from our Departments of Physics was co-author of the study. Her expertise centre on theoretical modelling and understanding what these findings mean for existing accretion rate models.
For her the findings offer a fascinating indication that existing models, used in astronomy for nearly 50 years, need re-writing.
The speed of the transition suggests that our understanding of how gas behaves around supermassive black holes is still incomplete. Excitingly - we need to develop new models to explain the phenomena we are seeing in this study.
The researchers will continue to monitor ESO 511-G030 to understand what triggers the rapid rebrightening and whether such behaviour is common among other supermassive black holes.
