Black Holes May Have 'Hair' That Poses Challenge To Key Theory Of Gravity, Physicists Say

10/01/2013 10:19 am ET

Physicists have been puzzling over black holes for decades now, and while standard theories hold that the mysterious objects are "bald," new research suggests that black holes actually have "hair."

Not the stuff that grows on your head, but detailed features that reveal the type of matter that fell into the black hole in the first place -- and that help scientists tell black holes apart.

Dr. John Wheeler, the physicist who coined the term "black hole," suggested that all it takes to define one is mass, angular momentum (how fast they spin) and electrical charge -- and that there are no other distinguishing physical features, or "hair." Then New Zealand mathematician Dr. Roy Kerr used Einstein's equations to describe this model mathematically.

But an international team of scientists came to a new conclusion when they used different theories of gravity -- called "scalar-tensor theories" -- to carry out a series of calculations on the theoretical structure of black holes.

"We used some techniques that allowed us to study the structures of black holes in these theories and we found that these black holes develop scalar hair when they are surrounded by ordinary matter," Dr. Thomas Sotiriou, a physicist at the International School for Advanced Studies in Italy, told The Huffington Post in an email. "This does not happen in the standard picture. "

Sotiriou said in a written statement that the hair anchors the black hole to surrounding matter in space, and that the hair's growth "is accompanied by the emission of distinctive gravitational waves." Observations from instruments like interferometers, which record gravitational waves, may help back up the research team's hypothesis, Sotiriou said.

Fascinating, but why does it matter?

"If black holes have... hair, this could be a smoking sign that general relativity (Einstein's theory and a remarkable achievement of mankind) is not the ultimate theory of gravity after all," Dr. Vitor Cardoso, another researcher on the team and a physics professor at the University of Lisbon's Instituto Superior Técnico in Portugal, told HuffPost Science in an email. "So, the quest is really for the correct theory of gravity, and whether general relativity still correctly describes the region close to black holes."

The research findings were published online September 10, 2013 in Physical Review Letters.

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