The influential "no-hair" conjecture suggests that black holes may be characterized by only three conserved parameters: mass, charge and angular momentum. However, counterexamples in which the conjecture fails are well-known in the literature. In this essay we study such Einstein-matter theories in which hairy black-hole configurations have been discovered. In particular, we analyze the spatial behavior of the matter fields which reside outside the black-hole horizon. We prove a theorem which reveals the central role played by the null circular geodesic (the "photonsphere") of such hairy black holes. According to this theorem, the asymptotic decline of the hair outside the horizon cannot start before the black-hole photonsphere is crossed. We therefore conclude that hairy black holes must have long hair which extends beyond the photonsphere.
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