The Flash Spectrum of the Sun . ... Explanation: In a flash, the visible spectrum of the Sun changed from absorption to emission on March 9 during the total solar eclipse. ... What remains, spread by the diffraction grating into the spectrum of colors to the right of the eclipsed Sun, are individual eclipse images. ... In between, the bright yellow emission image is caused by atoms of Helium, an element only first discovered in the flash spectrum of the Sun . ...