penumbrat

A penumbra is a term used in astronomy and optics to describe the region of partial shadow that surrounds the darkest part of a shadow, called the umbra. This occurs when the light source is not a perfect point source, but rather has a finite size. In the case of a solar eclipse, the penumbra is the area where the Sun is only partially blocked by the Moon. From within the penumbra, the Sun would appear as if a bite has been taken out of it.

The size and shape of the penumbra depend on the relative sizes of the light source and the object casting the shadow, as well as the distance between them. For a solar eclipse, the penumbra is a cone-shaped region that tapers away from the Earth. Observers within this region will experience a partial eclipse. The extent of the partial eclipse depends on how deep into the penumbra they are. Those at the edge of the penumbra will see very little of the Sun obscured, while those closer to the path of totality will see a larger portion of the Sun covered.

The concept of a penumbra is also relevant in other contexts, such as the shadow cast by an object illuminated by a broad light source in everyday life. While we may not always consciously distinguish between the umbra and penumbra in casual observation, the penumbra is always present when the light source has a discernible area.