Black holes are extremely massive and compact objects found in the Universe, that exert strong gravitational pull on neighbouring stars and on the gas disks that surround them. This effect on neighbouring bodies is, in fact, the only evidence for their existence, since black holes have never been directly seen. Black holes are believed to play a central role in many astrophysical processes, from the evolution of stars and galaxies to powering active galactic nuclei.
The prevailing paradigm in astrophysics is that the myriad of black holes in the cosmos is well described by just two physical properties: mass and angular momentum (a measure of its amount of rotation). This paradigm was summarised in 1971 by the physicist John Wheeler as “Black holes have no-hair” – a mantra that has stood the test of time.
But University of Aveiro physicists Carlos Herdeiro and Eugen Radu, a 2012 FCT Investigator, have unveiled a mechanism whereby some types of matter may create “hairy” black holes. This new type of black hole is predicted to have very different physical properties to the conventional ones; a prediction that may be verified through astrophysical observations of the interactions between black holes and the gas that surrounds them or their neighbouring stars.