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Glossary term: Lunar Eclipse

Description: A lunar eclipse occurs when the Moon passes into the shadow of Earth. This can only happen when the Sun, Earth, and Moon are very closely aligned, with Earth directly between the Sun and the Moon. As such, a lunar eclipse can only occur on the night of a full moon. A total lunar eclipse occurs when the Moon is fully within the shadow of Earth. A partial lunar eclipse occurs when the Moon is only partially covered by the shadow of Earth. The type and length of a lunar eclipse depends on the precise location of the Moon in its orbit around Earth at the time of the eclipse.

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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".

Related Media


Two astronomers view a lunar eclipse. Between them in the partly cloudy sky, a series of bright circles trace a curved path

The Eclipse Between Us, by Muhammad Rayhan, Indonesia

Caption: Second place in the 2021 IAU OAE Astrophotography Contest, category Total lunar eclipse. Total lunar eclipses belong to the rather spectacular celestial events and can be observed easily with and without a telescope. Here we see the stages of the total lunar eclipse of 31.1.2018 photographed in Indonesia: starting with the entry of the full moon disk into Earth's round umbra, the totality as Blood Moon, and the beginning of the Moon's exit from Earth's umbra until moonset.
Credit: Muhammad Rayhan/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


The Moon behind jagged, snowy mountains. The lower two thirds of the Moon are darker and redder than the upper third

The eclipsed Moon sets near the Rochetta di Prendera, Dolomiti Unesco, by Alessandra Masi, Italy

Caption: First place in the 2021 IAU OAE Astrophotography Contest, category Total lunar eclipse. A lunar eclipse occurs when the full moon moves into the Earth`s shadow. This is the case when the Sun, Earth and Moon are exactly or very closely aligned. The reddish light reflected from the lunar surface is caused by sunlight that has been refracted on its way through Earth´s atmosphere in the direction of the Moon. It appears reddish because of the Rayleigh scattering of bluer light. The round shape of the Earth's shadow visible on the lunar surface was a proof for Aristotle that the Earth must be a sphere. This photo shows the eclipsed Moon that sets near the Rochetta di Prendera, Dolomiti Unesco, Italy, on 21 January 2019.
Credit: Alessandra Masi/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons