Black holes can’t be formed from pure light. Quantum physics would curb their creation under any foreseeable conditions, a new study suggests.

Typically, matter is responsible for black holes. They’re often formed when a star’s core implodes at the end of its life. But matter isn’t necessarily required to form a black hole. According to Einstein’s general theory of relativity, black holes could form from concentrated energy alone.

A black hole formed from electromagnetic energy — that is, light — is called a kugelblitz. That concept has been jangling around in physicists’ brains for decades. But actually producing a kugelblitz seems to be a no-go, theoretical physicist Eduardo Martín-Martínez and colleagues report in a paper accepted to Physical Review Letters. “No known source in the current universe would be able to produce it, neither artificial or natural,” says Martín-Martínez, of the University of Waterloo in Canada.