The fat, doughnut-shaped clouds of dust that surround about half of supermassive black holes could be the remnants of planets and asteroids that have smashed into each other at incredible speeds.
An international team of astronomers says the mysterious clouds of dust could have the same cause as the so-called zodiacal dust in our own solar system, which is known to originate from collisions between solid bodies such as asteroids and comets.
Their theiry proposes that the central regions of galaxies contain not only black holes and stars but also planets and asteroids. Collisions between these rocky objects would occur at speeds as high as 1,000 km per second, progressively shattering them into microscopic dust.
"Too bad for life on these planets, but on the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy,” says Dr Sergei Nayakshin of the University of Leicester.
"This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy."
Nayakshin believes that understanding the origin of the dust near black holes is important in our models of how the black holes grow and how exactly they affect their host galaxies.
"We suspect that the supermassive black hole in our own galaxy, the Milky Way, expelled most of the gas that would otherwise turn into more stars and planets," he says.
"Understanding the origin of the dust in the inner regions of galaxies would take us one step closer to solving the mystery of the supermassive black holes."