Limb darkening refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image. Limb darkening occurs as the result of two effects:
Crucial to understanding limb darkening is the idea of optical depth. An optical depth of unity is that thickness of absorbing gas from which a fraction of 1/e photons can escape. This is what defines the visible edge of a star since it is at ...
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Limb darkening refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image. Limb darkening occurs as the result of two effects:
Crucial to understanding limb darkening is the idea of optical depth. An optical depth of unity is that thickness of absorbing gas from which a fraction of 1/e photons can escape. This is what defines the visible edge of a star since it is at an optical depth of unity that the star becomes opaque. The radiation reaching us is closely approximated by the sum of all the emission along the entire line of sight, up to that point where the optical depth is unity. When we look near the edge of a star, we cannot "see" to the same depth as when we look at the center because the line of sight must travel at an oblique angle through the stellar gas when looking near the limb. In other words, the solar radius at which we see the optical depth as being unity increases as we move our line of...
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