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Glossary term: Solar Eclipse

Description: A solar eclipse occurs when the Earth, Moon, and the Sun are arranged in a straight line, with the Moon between Earth and the Sun. When observed from the surface of the Earth, the disk of the Moon covers the disk of the Sun in the sky; from space we can see the shadow of the Moon moving across the sunlit side of the Earth.

There are different types of solar eclipses. Total, when the disk of the Moon completely covers the Sun; partial, when only a fraction of the solar disk is covered even at maximum eclipse; and annular, when the Moon is farther away than average and hence appears smaller than usual allowing a ring of the solar disk to remain visible even at the maximum extent of the eclipse.

During a total solar eclipse, the darkest point of the shadow of the Moon on Earth is called the "umbra", and the edge of the shadow is called the "penumbra". Observers in the umbra see a total eclipse while observers in the penumbra see a partial eclipse.

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

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The Moon appears as a black circle, blocking light from the Sun. A faint glow from the Solar corona surrounds the Moon.

Total Solar Eclipse

Caption: This image represents the total solar eclipse as observed from Kurigram in Bangladesh. Solar eclipses occur when the moon, as seen from earth, passes in front of the Sun. The moon is much smaller than the Sun, it is closer by the night amount that the angular diameters of the Sun and moon are almost the same (~approximately 1/2 a fingertip). Therefore, the moon can cover up the Sun's disk when it passes directly between the Sun and the Earth. The ring of light around the black circle is called the corona.
Credit: Lutfar Rahman Nirjhar credit link

License: CC-BY-3.0 Creative Commons Attribution 3.0 Unported icons


The dark, irregular shape of Phobos crosses the lower portion of the Sun’s disk, obscuring roughly one quarter of it.

Transit of Phobos from Mars

Caption: This video shows the Sun viewed from Mars as Mars’ moon Phobos transits across the solar disk. This video is composed of images taken from the Martian surface on the 30th of September 2024 by the Mastcam-Z camera of NASA’s Perseverance Mars rover. While our Moon is perfectly sized to eclipse the Sun when seen from the Earth’s surface, Phobos’s size and orbit mean that it cannot cover the solar disk completely. This means that this event is a transit and not an eclipse. This video is in real time, with the entire transit lasting just 32 seconds. This compares with the several hours a solar eclipse on Earth takes from the Moon first obscuring part of the Sun to the Sun being completely visible again. This is due to Phobos’ much shorter orbital period of just over seven and a half hours compared to the Moon’s orbital period of 27 days as well as the solar disk appearing slightly smaller from Mars than it does from Earth. Note the non-spherical shape of Phobos as it crosses the solar disk.
Credit: NASA/JPL-Caltech/ASU/MSSS credit link

License: PD Public Domain icons


Over an observatory with several domes the Moons slowly covers the Sun leaving a thin, glowing ring.

A total solar eclipse over the La Silla Observatory, Chile

Caption: A real-time video showing the total solar eclipse on the 2nd of July 2019 over the La Silla Observatory in Chile. This video covers the moments before totality, the just under two minutes of totality, and the moments after totality. Note that at the start of the video the Sun was already almost completely obscured by the Moon, it is just hard to see due to the brightness of the Sun and the exposure of the camera. Indeed the Moon started partially eclipsing the Sun roughly an hour before the start of this recording and would continue to partially obscure the Sun for roughly the same time afterwards. At the point of totality one can see the faint glow of the Sun’s diffuse outer regions and on the horizon one can also see the glow from the parts of the surrounding areas on Earth that are not experiencing totality.
Credit: ESO/A. Santerne credit link

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


A large, circular shadow, about one half the width of North America slowly moves across the continent from south-west to north-east

2024 Total Solar Eclipse from Space

Caption: The NASA Deep Space Climate Observatory (DSCOVR) captured the total solar eclipse over North America on the 8th of April, 2024 from space using its Earth Polychromatic Imaging Camera (EPIC). This video shows images of Earth taken over the course of four and a half hours. The Moon’s shadow on the Earth can be seen as it moves from south-west to north east. While the shadow looks like it covers a huge part of the continent, only a strip up to 185 km wide in the middle of the eclipse's path saw a total eclipse at some point on this day and at any one time only the central part of the shadow would have experienced a total solar eclipse. Most of the area covered by this shadow only saw a partial eclipse. DSCOVR sits at L1, a stable gravitational point between the Sun and Earth and observes the day side of the Earth.
Credit: NASA/DSCOVR EPIC team/Michala Garrison and Wanmei Liang credit link

License: PD Public Domain icons


The Moon moves from top right to bottom right, covering then uncovering the Sun. At totality wispy features surround the Sun

Total Solar Eclipse from Casper, Wyoming, USA

Caption: This video shows the total solar eclipse of the 21st of August 2017 observed from Casper, Wyoming, USA by a team of astronomers from the European Space Agency (ESA). This video has been sped up considerably, in reality the moment of totality lasted just under two and a half minutes while the time from the Moon first appearing to obscure the Sun until the Sun was completely unobscured was two hours and 48 minutes. Before the eclipse we can see several sunspots on the Sun. The Moon moves across the Sun, covering the whole solar disk visible from the point on the Earth this video was taken from. At totality we can see the diffuse solar corona which is normally outshone by the bright solar disk. Note that while edges of the Sun appear brighter just before and just after totality, this is due to exposure time of the camera being adjusted to make the features visible at totality more obvious. Towards the end of the video some thin cloud begins to affect the observations.
Credit: Video credit: ESA/CESAR ; Music copyright: Flight Of The Angel 3 by Chris Blackwell, audionetwork.com credit link

License: CC-BY-SA-3.0-IGO Creative Commons Attribution-ShareAlike 3.0 IGO icons

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