The Sun appears yellow to us on Earth due to the scattering of light by our atmosphere. While the Sun itself emits white light, containing all the colors of the rainbow, our atmosphere preferentially scatters shorter wavelengths of light, like blue and violet. This leaves the longer wavelengths, such as yellow and red, to reach our eyes more directly.
The Sun's True Color: White
It's crucial to understand that the Sun's actual color is white. This is because it emits light across the entire visible spectrum. Sources like ScienceFocus and Reddit's r/Astronomy confirm this. The Sun's light peaks in the green part of the spectrum, but the combination of all visible wavelengths results in white light.
Atmospheric Effects: Why it Appears Yellow
The apparent yellow color is a result of Rayleigh scattering, a phenomenon where shorter wavelengths are scattered more effectively than longer ones. As described in the provided text, "Our atmosphere scatters shorter to bigger wavelengths color from sunlight when the white light travels through it. During day, it scatters violet and blue colors leaving yellowish sunlight (the reason why sky is blue and sunlight is yellow)." This scattering effect is why the sky appears blue – the blue light is scattered in all directions. The remaining light reaching our eyes appears yellowish.
Sunrise and Sunset: Red and Orange Hues
At sunrise and sunset, the Sun's light travels through a much longer path in the atmosphere. This increases the scattering effect, further removing the blue and green wavelengths, and leaving primarily the longer red and orange wavelengths. This is why the Sun often appears red or orange at these times. The NASA Eclipse 2017 website touches upon the relationship between surface temperature and perceived color, noting that lower temperatures could shift the peak of the spectrum towards yellow, orange, or even red.
Sun's Spectral Class: Yellow Dwarf
The Sun is classified as a G-type main-sequence star, often referred to as a "yellow dwarf." However, this classification is based on the peak wavelength of its emitted light, not its perceived color from Earth. As explained on Quora, this classification reflects its spectral characteristics and position within the Hertzsprung-Russell diagram, not our visual perception.
In Summary
The Sun's color is white, but it appears yellow to us due to atmospheric scattering. The amount of scattering varies depending on the Sun's position in the sky, resulting in different colors at different times of day.
