täysivarjo

Täysivarjo is a Finnish term that translates to "total shadow" or "umbra." In astronomy, it refers specifically to the darkest, innermost part of a shadow cast by an opaque object, such as a celestial body, when illuminated by a light source. This is in contrast to the penumbra, which is the lighter, outer part of the shadow where the light source is only partially obscured.

During a solar eclipse, the täysivarjo is the region on Earth's surface where the Sun is completely blocked by the Moon. Observers within the täysivarjo experience a total solar eclipse, witnessing the Sun's corona. The path of the täysivarjo across the Earth's surface is known as the path of totality, and it is a relatively narrow band.

The concept of täysivarjo is also relevant in other contexts where shadows are formed. For instance, when a planet casts a shadow in space, the täysivarjo is the region of complete darkness. Understanding the properties and extent of the täysivarjo is crucial for predicting and observing phenomena like eclipses and for calculating the illumination of celestial bodies. The shape and size of the täysivarjo depend on the relative sizes of the light source and the object casting the shadow, as well as their distances.