Testing the No-Hair Theorem with Sgr A*

Figure 4

Images of rings of light of (a) a Kerr and (b) a quasi-Kerr black hole at an inclination cos𝑖=0.25. Increasing values of the spin cause a displacement of the ring in the image plane, but the ring remains (nearly) circular for values of the spin 𝑎≲0.9 M (a). Nonzero values of the deviation parameter 𝜖 (b) lead to an asymmetric ring image [23].

(a)

(b)