Spindle Black Hole: The Shadow Changes Shape express
At the center of attention is a black hole of unusual shape. Its geometry resembles a spindle: a slight elongation is added to the usual rotation. The parameter B measures this deformation.
The motion of particles changes. For massive bodies, the inner stable circular orbit (ISCO) shifts, and an outer stable orbit (OSCO) appears — something that did not exist before. Light rays (photons) behave differently: their trajectories could only be separated into parts approximately, to first order in B². This allowed constructing the photon region and the black hole shadow.
Numerical verification confirmed that the shadow indeed differs from the Kerr one. The deviations are small but noticeable, like a familiar silhouette slightly stretched in one direction.
The deformation parameter B is so small that the shadow is almost indistinguishable from the Kerr one to the naked eye, but precise measurements can catch the difference.