Glossary term: Penumbra

Description: The penumbra (Latin for "almost shadow") has two meanings.

In the first, penumbra refers to the outer, less dark, part of the shadow cast onto a body during an eclipse, in which the light is only partially blocked. For example, in a solar eclipse, observers in the penumbra region will see the Moon only partially cover the Sun and experience a partial eclipse only.

In the second, penumbra refers to the distinct outer and brighter part of a sunspot.

Related Terms:

See this term in other languages

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".