Limb darkening
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Limb darkening is an optical effect seen in stars and planets, where the central part of the disk appears brighter than the edge, or limb. Its understanding offered early solar astronomers an opportun
A filtered image of the Sun in visible light, showing the limb-darkening effect as a dimmer luminosity towards the edge or limb of the solar disk. The image was taken during the 2012 transit of Venus (seen here as the dark spot at the upper right).
Solar corona
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The solar corona is the outermost layer of the Sun's atmosphere. It is a region filled with relatively hot, tenuous plasma that is structured by the solar magnetic field.
Limb darkening
…far-infrared or radio wavelengths. Above the lower atmosphere, and well above the temperature-minimum region, the Sun is surrounded by the million-kelvin solar corona. For most wavelengths this region is optically thin, i.e. has small optical depth, and must, therefore, be limb-brightened if it is spherically symmetric…
During a total solar eclipse, the Sun's corona and prominences are visible to the naked eye.
Temperatures in the solar atmosphere rise precipitously with height in the transition region between the chromosphere and corona.
The light visible close to the Sun during a total solar eclipse originates primarily from the K-corona.
The zodiacal light from sunlight scattered by interplanetary dust merges with the F-corona close to the Sun.