penumbrální
Penumbral is a term that refers to the partial shadow cast by an opaque object when the light source is not entirely obscured. This shadow is less dark than the umbra, which is the region where the light source is completely blocked. In the context of a solar eclipse, the penumbra is the area on Earth where the Moon only partially covers the Sun. Observers within the penumbra will see a partial eclipse, while those within the umbra experience a total eclipse.
The shape and size of the penumbra depend on the relative sizes of the light source and
In astronomy, understanding the penumbra is crucial for predicting and observing eclipses and other shadow phenomena.