Astronomy. The lighter periphery of a sunspot, surrounding the dark core or umbra.
| 单词 | θ902 | 
| 释义 | the world > the universe > sun > solar activity > 			[noun]		 > mark on sun > sunspot > light part of (2)		 penumbra1763 Astronomy. The lighter periphery of a sunspot, surrounding the dark core or umbra. umbra1788 Astronomy. In sun-spots: (see quots.). | 
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