Earth  Sun  Planets and Moons  ID: 4910

2021 Annular Solar Eclipse

On Thursday, June 10, 2021, the Moon passes in front of the Sun, casting its shadow across Canada and the Arctic.

This is an annular (ring) eclipse — not to be confused with annual. At the time of the eclipse, the Moon is too far away from the Earth, and therefore too small in the sky, to completely cover the Sun. The central part of the shadow, where the silhouette of the Moon is completely surrounded by a ring of sunlight, is called the antumbra. The part of the shadow outside the antumbra, where observers see a partial eclipse, is the penumbra.

In the animation, the antumbra is the small black oval. The streak it leaves in its wake is the path of annularity. Anyone within this path will see the annular ring effect when the antumbra passes over them. Steps in the shading denote different percentages of Sun coverage (obscuration), at levels of 80%, 60%, 40% and 20%. The images of the Sun show its appearance at a number of locations during the eclipse, each oriented to the local horizon.

The numbers in the lower left corner give the latitude and longitude of the center of the antumbra as it moves, along with the altitude of the Sun above the horizon at that point. Also shown is the duration of annularity: for anyone standing at the center point, this is how long the ring effect will last. When these numbers are missing, the center of the shadow cone isn't touching the Earth.

The map shows the global extent of the shadow during the eclipse. The antumbra is drawn at 10-minute intervals. The elongated shape is caused by the glancing angle of the Moon's shadow during this eclipse. The green lines (isochrons) are an indication of where the shadow is at different times. Everyone on those lines is experiencing their local maximum eclipse at the indicated times.

The following table lists some of the constants and data used to create these media items.

Earth radius6378.137 km
Earth flattening1 / 298.257 (the WGS 84 ellipsoid)
Moon radius1737.4 km (k = 0.2723993)
Sun radius696,000 km (959.634 arcsec at 1 AU)
EphemerisDE 421
Earth orientationSOFA library iauC2t06a()
Delta UTC69.184 seconds (TT – TAI + 37 leap seconds)
ΔT69.363 seconds

A number of sources explain Bessel’s method of solar eclipse calculation, including chapter 9 of Astronomy on the Personal Computer by Oliver Montenbruck and Thomas Pflager and the eclipses chapter of The Explanatory Supplement to the Astronomical Almanac. The method was adapted to the routines available in NAIF's SPICE software library.

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Visualization Credits

Ernie Wright (USRA): Lead Visualizer
Sarah Frazier (SGT): Producer
Laurence Schuler (ADNET Systems, Inc.): Technical Support
Ian Jones (ADNET Systems, Inc.): Technical Support
Please give credit for this item to:
NASA's Scientific Visualization Studio

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Data Used:
Terra and Aqua/MODIS/Blue Marble: Next Generation also referred to as: BMNG
The Blue Marble data is courtesy of Reto Stockli (NASA/GSFC).
JPL DE421 also referred to as: DE421
Ephemeris - NASA/JPL
Note: While we identify the data sets used in these visualizations, we do not store any further details nor the data sets themselves on our site.

SVS >> Moon
SVS >> Solar Eclipse
GCMD >> Earth Science >> Atmosphere >> Atmospheric Radiation >> Solar Irradiance
SVS >> Hyperwall
SVS >> Eclipse
SVS >> Heliophysics
SVS >> Sun-Earth-Moon Interactions
SVS >> Sun and Earth
NASA Science >> Earth
NASA Science >> Sun
NASA Science >> Planets and Moons

GCMD keywords can be found on the Internet with the following citation: Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version