The surface of the Sun consists of hydrogen and helium, and trace quantities of other elements, including iron, oxygen, carbon, neon, and calcium. This is a subtractive effect, as the preferential scattering of shorter wavelength light removes enough violet and blue light, leaving a range of frequency that is perceived by the human eye as yellow. It's this scattering light at the blue end of the spectrum that gives the surrounding sky its color. When the Sun is low in the sky, even more light is scattered so the Sun appears orange or even red.

     A rare optical phenomenon may occur shortly after sunset of before sunrise, known as a green flash. The flash is caused by light from the sun just below the horizon being bent towards the observer. Light of shorter wavelenghts (violet, blue, and green) is bent more than that of longer wavelenghts (yellow, orange, and red) but the violet and blue light is scattered more, leaving light that is preveived as green.

     Althogh it is  the nearest star to Earth and has been intensivly studied by scientests, many questions about the Sun remain unanswerd. Current topics of scientific inquiry include the Sun's regular cycle of sunspot activity, the physics and orgins of flares and prominences, the magnetic interaction between the chromospheres and the corona, and the origin of solar wind.