Black Holes May Have 'Hair,' New Research Contests Old 'Bald' Theory

New research suggests that the physics behind a black hole may not be as cut and clean as previously thought.

The mathematical beauty of a black hole - the full nature of which can be described by just a handful of factors - prompted the physicist John Archibald Wheeler to coin the phrase "black holes have no hair," a digestible way of stating the traditional model of black hole construction: only mass, electric charge and angular momentum are needed to define the structures.

That hypothesis for a black hole's construction, known as the "bald" or "clean" theory, was developed by in 1963 by Roy Kerr. Since then, it has stood as the generally accepted theory for black hole construction.

But new research suggests that black holes may have a lot more metaphorical hair than previously believed.

"Black holes, according to our calculations, may have hair," said Thomas Sotiriou, a physicist at the International School for Advanced Studies in Italy.

"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," Sotiriou explains. "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."

Writing in the journal Physical Review Letters, Sotiriou and his colleagues contend that new observations of gravitational waves suggest at "hairier" model of black holes than previously believed.

"According to our calculations, the growth of the black hole's hair is accompanied by the emission of distinctive gravitational waves. In the future, the recordings by the instrument may challenge Kerr's model and broaden our knowledge of the origins of gravity," Sotiriou said.