London: The thick donut-shaped disks of gas and dust that surround most massive black holes in the universe are 'clumpy' rather than smooth as originally thought, says a study co-authored by an Indian-origin researcher.
Donuts around supermassive black holes were first proposed in the mid-1980s to explain why some black holes are hidden behind gas and dust, while others are not.
The new research is important for understanding the growth and evolution of massive black holes and their host galaxies.
Until recently, telescopes were not able to penetrate some of these donuts, also known as tori, which feed and nourish the growing black holes tucked inside.
The study co-authored by Poshak Gandhi of the University of Southampton in Britain, described results from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's XMM-Newton space observatory.
With its X-ray vision, NuSTAR recently peered inside one of the densest tori known around a supermassive black hole.
This black hole lies at the centre of a well-studied spiral galaxy called NGC 1068, located 47 million light-years away in the Cetus constellation.
The observations revealed that the rotating material is not a simple, rounded donut but more like defective, lumpy donuts that a donut shop might throw away.
The new discovery is the first time that this clumpiness has been observed in an ultra-thick donut, and supports the idea that this phenomenon may be common, the study said.
The findings appeared in the journal Monthly Notices of the Royal Astronomical Society.