Question

an event in which the shadow of one celestial object falls on another celestial object
umbra
penumbra
eclipse
solar eclipse

Explanation:

An eclipse is defined as an event where the shadow of one celestial object falls on another. The term "umbra" refers to the darkest part of a shadow, "penumbra" is the lighter part of a shadow, and "solar eclipse" is a specific type of eclipse involving the Sun. Since the question is about the general event (not a specific type like solar) and the definitions of umbra and penumbra are about parts of a shadow (not the event itself), "eclipse" fits best.

Answer:

eclipse