What Is Doppler Imaging?

A method of "imaging" the surface of a star by using the principle that the rotation of the star causes its spectral line to widen due to Doppler shift. Because the stars are very far away, people have not been able to directly observe the characteristics of the stars. But the spectral distortion caused by the features on the surface of the star (such as sunspots) will shift and change left and right with the Doppler shift of the star's rotation. Based on the observation of high-resolution star spectral contours, the images of star surface features can be analyzed by inversion. In this way, the phenomenon of large sunspots on many stars has been determined.