Limb darkening is a darkening of the solar limb at optical wavelengths, arising because the observer's line of sight passes through shallower, cooler, and more absorbing layers of the photosphere as it moves away from the center of the Sun's disk; a similar effect occurs with Jupiter and with the members of eclipsing stars as they move in front of each other, and has been detected in the case of several single stars, including Hamal. Limb brightening is a brightening of the solar limb at X-ray, extreme ultraviolet, and radio wavelengths, due to the observer's line of sight intercepting more of the hot inner corona and less of the cooler photosphere as it moves away from the center of the Sun's disk.