  We study the shadow cast by a large gravitating sphere, similar to our Sun.
For this, we consider the gravitational field produced by a static mass
monopole within the first post-Newtonian approximation of the general theory of
relativity. We study the propagation of a monochromatic electromagnetic wave in
the vicinity of a large, opaque, gravitating sphere. To treat the opaque nature
of the body and its physical size, we implement fully absorbing boundary
conditions and develop a wave-optical treatment of the shadow formed by this
object. Based on this approach, we demonstrate that the structure of the shadow
is determined by the Schwarzschild radius of the body and its physical size.
The shadow's boundary has the shape of a concave rotational hyperboloid bent
inward due to the refractive properties of the curved spacetime. We show that
there is no light in the shadow. However, even in the presence of gravity and
related gravitational bending of photon trajectories there is the bright spot
of Arago that is formed behind a perfectly spherical obscuration.
