The birth of the active helium core is called the helium flash. The Sun as a red giant will fuse helium for about 2 billion years after the helium flash. The Doppler effect shifting light wavelengths to the red end of the spectrum because of the motion of the source. A red shift indicates a receding source of light, with the magnitude of the shift corresponding to the velocity of the source. Astronomers relate red shifts to a calibrated distance in order to stretch their cosmic yard stick beyond the local realm of galaxies.
Planetary astronomers observe small red shifts and blue shifts in stars that unseen planets orbit .
Raindrops refract light into rainbows. A prism behaves the same way using glass instead of water. The refraction happens at the boundary between two different, transparent materials. Normally planets progress west to east along the ecliptic . The position of a celestial object in the sky east of the vernal equinox along the celestial equator .