Comparing Shadows of Blackhole and Naked Singularity

Understand

It is now theoretically well established that not only a black hole can cast shadow, but other compact objects such as naked singularities, gravastar or boson stars can also cast shadows.

• An intriguing fact that has emerged is that the event horizon and the photon sphere are not necessary for a shadow to form.
• Now, when two different types of equally massive compact objects cast shadows of same size, then it would be very difficult to distinguish them from each other.
• However, the nature of the nulllike and timelike geodesics around the two compact objects would be different, since their spacetime geometries are different.