Black holes may not be as simple and "clean as portrayed in Roy Kerr's 1963 "clean" black hole model and researchers speculate that these cosmic bodies may actually have "hair."

In 1963, Roy Kerr proposed a "clean" black hole model, which till date serves as a theoretical paradigm for all black holes. However, in a new study conducted by researchers from the International School of Advanced Studies (SISSA), Trieste, and IST, Lisbon, evidence has surfaced, which suggests these black holes are not as clean as previously believed and might actually have hair.

Mass and angular momentum are two quantities used to describe black holes in Kerr's traditional model. Once a star collapses at the end of its life cycle, its memory is lost. All that is left of the star is a black hole that has no distinctive characters, i.e. all black holes have approximately the same mass and angular momentum.

However, according to the new study, researchers claim that this might not be the exact way that things take place. According to Thomas Sotiriou, a physicist at the International School for Advanced Studies (SISSA) of Trieste, black holes many have "hair." This statement contradicts John Wheeler's earlier claims that said "black holes have no hair" by which he meant that mass and angular momentum are all one needs to properly define black holes.

"Although Kerr's 'bald' model is consistent with General Relativity, it might not be consistent with some well known extensions of Einstein's theory, called tensor scalar theories" said Sotiriou.  "This is why we have carried out a series of new calculations that enabled us to focus on the matter that normally surrounds realistic black holes, those observed by astrophysicists. This matter forces the pure and simple black hole hypothesized by Kerr to develop a new 'charge' (the hair, as we call it) which anchors it to the surrounding matter, and probably to the entire Universe."

Findings of the new study also claim that the growth of this "hair" also causes emission of distinctive gravitational waves.  Sotiriou said that further studies on the matter may lead to certain changes in Kerr's traditional black hole model.