Limb Darkening

The limb darkening phenomenon is a decrease in brightness at the edge (the limb) of the surface of a star or planet. The effect is best studied on the Sun, but has also been put in evidence on other stars. It gives to an image of the Sun the appearance of a sphere illuminated by the observer with a gradual shading on the edge (see Fig. 1). For a star, it occurs because the light at the edge comes on average from cooler - and thus less bright - layers of the photosphere. Jupiter also exhibits a limb darkening effect. The limb darkening effect is actually observed when detecting planets by the transit method and must be taken into account