That part of the Moon’s shadow that extends beyond the umbraA complete shadow (as of the Moon or the Earth) within which the source of light (the Sun) is totally hidden from view. Also, the dark inner area of a sunspot.. An annular eclipseA solar eclipse that occurs when the apparent size of the Moon is not large enough to completely cover the Sun. A thin ring of very bright sunlight remains around the black disk of the Moon. is seen by an observer in the antumbra.