Spinning Black Holes May Grow Hair

New simulations of the dynamics of spinning black holes by William East from the Perimeter Institute for Theoretical Physics, Canada, and Frans Pretorius from Princeton University, New Jersey [1], have shed light on an intriguing possibility. If there exists in nature a bosonic particle with an exceptionally small mass(<10−10eV∕c2) then a black hole may spontaneously grow “long hair,” in the form of highly amplified excitations of the field that are trapped in the vicinity of the black hole (Fig. 1). The finding suggests that black holes may grow hair that is long-lived and extends well beyond the black hole event horizon. This conclusion poses a challenge to the cherished “no-hair” paradigm. It also raises the possibility that black holes with hair, if they exist, may one day be detected via their gravitational-wave signatures.