Sun  Planets and Moons  ID: 4424

March 2016 Eclipse Shadow Cones

A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is completely blocked by the Moon, and anyone inside the umbra sees a total eclipse. Within the larger penumbra, the Sun is only partially blocked.

In this animation, the umbra and penumbra cones are viewed through a telescopic lens on a virtual camera located far behind the Moon. Long focal lengths like the one used here appear to compress the distance between near and far objects. Despite appearances, the geometry of the scene is correct. The Earth is roughly 104 lunar diameters beyond the Moon, and the angle at the apex of the umbral cone is only about half a degree.

From this point of view directly behind the Moon, the edges of the shadow cones look circular. The edge of the penumbra is outlined in yellow. It passes over Southeast Asia, Australia, and southern China before crossing the Pacific Ocean and reaching Hawaii. The path of the umbra (the small black dot) leads through Indonesia and over the tiny Woleai atoll in Micronesia.

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Visualization Credits

Ernie Wright (USRA): Lead Visualizer
Genna Duberstein (USRA): Producer
Please give credit for this item to:
NASA's Scientific Visualization Studio

The Blue Marble data is courtesy of Reto Stockli (NASA/GSFC).

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Data Used:
LRO/LOLA/Digital Elevation Map
LRO/LROC/WAC 643nm High Sun Global Mosaic
Terra and Aqua/MODIS/Blue Marble: Next Generation

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