Researchers have calculated the rate at which matter falls onto Sagittarius A*, the Milky Way's central black hole.
One thousandth of the matter flowing into the Milky Way from the intergalactic medium makes it all the way down and into the hole.
Over the last quarter-century, astrophysicists have recognised the close, dynamic relationship that exists between many galaxies and black holes.
"What surprised me was how important black holes are as shapers and controllers of how galaxies evolve."
These massive holes — concentrations of matter so dense that gravity prevents even light from escaping — act as galaxies' engines.
In a feedback process, energy is spat back out into the galaxy as the black hole engulfs this matter (either in dribs and drabs or in sudden bursts).
Researchers have only hazy ideas about the "active" episodes that transform supermassive black holes into so-called active galactic nuclei.