Black holes aren't what they eat. Einstein's general relativity predicts that no matter what a black hole consumes, its external properties depend only on its mass, rotation and electric charge.

All other details about its diet disappear.

Astrophysicists whimsically call this the no-hair conjecture. (Black holes, they say, "have no hair.")

There is a potentially hairy threat to the conjecture, though. Black holes can be born with a strong magnetic field or obtain one by munching on magnetized material. Such a field must quickly disappear for the no-hair conjecture to hold.

But real black holes don't exist in isolation.

They can be surrounded by plasma—gas so energized that electrons have detached from their atoms—that can sustain the magnetic field, potentially disproving the conjecture.

Source

All other details about its diet disappear.

Astrophysicists whimsically call this the no-hair conjecture. (Black holes, they say, "have no hair.")

There is a potentially hairy threat to the conjecture, though. Black holes can be born with a strong magnetic field or obtain one by munching on magnetized material. Such a field must quickly disappear for the no-hair conjecture to hold.

But real black holes don't exist in isolation.

They can be surrounded by plasma—gas so energized that electrons have detached from their atoms—that can sustain the magnetic field, potentially disproving the conjecture.

Source