penumbra

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penumbrasearch for term: 1) A partial shadow cast by the Earth or Moon that surrounds the umbra, or total shadow. During a total lunar eclipse, the Moon passes through the Earth's penumbra, then into the umbra where the Moon "disappears". Similarly, during a total solar eclipse, the Earth passes through the Moon's penumbra, and then into its umbra.

2) The region immediately surrounding the darkest portion, or umbra, of a sunspot. This region is darker and cooler than the surrounding photosphere, but lighter and hotter than the center of the sunspot.