The sun is often depicted as yellow, but scientifically, its true color is white. This difference arises from how the sun emits light and how that light interacts with Earth’s atmosphere before reaching our eyes.
The Sun’s True White Light
The sun is a G2V star. Its surface, the photosphere, maintains a temperature of 5,778 Kelvin. This temperature causes the sun to emit light across the entire electromagnetic spectrum.
Within the visible spectrum, the sun emits all colors: red, orange, yellow, green, blue, indigo, and violet. While its peak emission is in the blue-green part of the spectrum, it emits significant amounts of all visible wavelengths. When these colors are present in roughly equal proportions, they combine to form white light. Therefore, an observer viewing the sun from space would perceive it as white.
The Role of Earth’s Atmosphere
The sun appears yellow from Earth due to Rayleigh scattering. Earth’s atmosphere, primarily nitrogen and oxygen molecules, contains particles much smaller than visible light wavelengths. When sunlight enters the atmosphere, shorter wavelengths like blue and violet are scattered more efficiently than longer wavelengths like red and yellow.
This scattering disperses blue and violet light across the sky, making the sky appear blue. The remaining sunlight reaching our eyes has less blue and violet light, leaving a greater proportion of yellow and red, which makes the sun appear yellow. At sunrise and sunset, light travels through more atmosphere, increasing blue light scattering and allowing more red and orange wavelengths to reach our eyes, creating vibrant hues.
Our Eyes and the Perception of White
Our visual system influences how we perceive color. The retina in our eyes contains cone photoreceptors, sensitive to red, green, and blue light. When all visible wavelengths are present in relatively equal amounts, these cone cells are stimulated in a balanced way, and our brain interprets this as white.
Even though atmospheric scattering removes some blue light, the sun still emits a broad spectrum of colors. The remaining mixture, processed by our eyes and brain, is perceived as yellow, not its true white. This highlights that our perception of color is not simply a direct reflection of light’s physical properties but also an interpretation by our sensory organs and brain.