The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra's cast. These names are usually used when referring to the shadows cast by celestial bodies. Umbra The umbra (Latin for "shadow")'s the darkest part of the shadow. From within the umbra, the source of light's completely concealed by the occulting body. In astronomy, an observer in the umbra's said to be in the shadows experiencing total eclip… (More on Antumbra)