There are many ways for a star to meet its end: suddenly and spectacularly, as a supernova; gradually and gracefully, as a white dwarf wreathed in a planetary nebula; and gruesomely, torn apart by a black hole. Tidal disruption events, in which a star gets too close to a black hole and is ripped apart by tidal forces, play out over the course of months or years in galaxies across the universe.
First predicted by theorists in the 1970s, these events are now commonly observed. Researchers led by PhD candidate Zheng Cao of Radboud University and the Netherlands Space Research Organization SRON studied such an event with multiple X-ray satellites. From variations in the X-ray emission, the researchers have deduced that the gas of the star being ripped apart is falling into the black hole, slowly but surely. The rotation and gravity of the black hole dictates how this infalling happens. From the X-ray variations, they deduce how massive the black hole is, and how quickly it rotates around its axis.
Knowledge of massive black holes is now quickly advancing because ever more of these events are detected. The American Astronomical Society issued a special Halloween article focussing on these graveyards of shredded stars.