Glossary term: Umbra

Description: Umbra is Latin for "shadow". In the context of eclipses, the umbra is that region of space where an observer sees the one body block the other's light completely. For a solar eclipse, for instance, any observer in the umbra will see the Sun's disk covered completely by the disk of the Moon. An observer located in the penumbra region, on the other hand, will only see a partial eclipse – in the case of a solar eclipse, the Sun's disk covered only partially by the Moon. If an observer sees the covering object as too small to cover the object behind it completely, as in an annular solar eclipse, the observer is said to be in the antumbra. Alternate meaning: the inner, darker region of a sunspot is called its umbra, the surrounding less dark region its penumbra.

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".