When surrounded by gas and dust, black holes don't just immediately start drawing everything toward them and consuming it. Instead, this matter forms a flattened, fast-moving structure called an accretion disk around the black hole.
Black holes grow when rapidly spinning disk material gradually moves from the disk's outer edge to the inner edge closest to the black hole. From there, it is gradually "fed" to the black hole's event horizon — the point beyond which nothing, not even light, can escape the hole's gargantuan gravitational influence.
Matter within the accretion disk is violently heated by immense tidal forces, causing many accretion disks to glow brightly. This makes detecting accretion disks one of the easiest ways for astronomers to locate black holes.
Black holes can also swallow stars, but only the most massive objects can swallow a star whole, according to Hubblesite. More often, when a black hole feeds on a star, it stretches and squashes it with tidal forces first, in a process called spaghettification or a tidal disruption event (TDE).
"A TDE is basically what happens when a star wanders too close to a supermassive black hole and gets torn apart by the tidal forces surrounding that black hole," Yvette Cendes, a radio astronomer at the Harvard & Smithsonian Center for Astrophysics, told Live Science. "The unbinding of the star is actually very fast. That process is like a few hours, tops."
Traditional models of TDEs suggest that half of this spaghettified stellar material gets flung outward, away from the black hole, Cendes added. The other half forms an accretion disk — or joins an existing one — with the destructive black hole at its center. The stellar material is further broken apart by the violent conditions in the accretion disk and is also gradually fed to the event horizon.