We often forget that there are 2 kinds of speeds. The linear speed and the angular speed. The angular speed is not defined by distance but angle which is why its a properness (in the proper-frame?) and same as the frequency or rotation in a PLANE that does not move. eg the sun does not move when light is exuberant. Light comes out perpendicular to that unmoving surface. But the surface has the angles which keep on rotating to give us angular deflections. The rate at which the angle moves is the frequency of light where as the rate at which the distance is covered perpendicular to the surface that does not move is the speed or speed of light. Which is why due to high intensity we see the sun to be a circular flame (because frequency is so high that the angles are rotating really fast and we see a circle on the face of the sun) But the stars that are too far away they twinkle because these rotation on its face are slow. The frequency of light is small because the energy or intensity is low. So you see twinkles. But light is still moving at the same speed towards us. It takes 4.5 years from some stars while taking 8 minutes from sun, both at the same speed. But with sun, the face of the sun or angles on face of sun are rotating really fast. That rotation gives us the energy and momentum but the speed at which they all move is still c.
Why Sun is circular but star twinkles?