Many people imagine the Sun as a vibrant yellow or fiery orange orb. This common perception influences how we depict our star. However, the Sun’s actual color, from a scientific standpoint, is quite different from what we typically observe.
The Sun’s Actual Color
When viewed from space, beyond Earth’s atmosphere, the Sun appears distinctly white. This is because the Sun emits light across the entire visible electromagnetic spectrum in roughly equal proportions. When all these colors combine, they create what our eyes perceive as white light. While the Sun’s peak emission is in the green-to-yellow part of the spectrum, this broad emission across all visible wavelengths results in white light.
Why the Sun Appears Yellow
The Sun often appears yellow, orange, or red from Earth due to Rayleigh scattering. Earth’s atmosphere contains tiny gas molecules, primarily nitrogen and oxygen, which are much smaller than visible light wavelengths. When sunlight enters the atmosphere, these molecules scatter light in different directions. Shorter wavelengths, such as blue and violet, scatter much more efficiently than longer wavelengths like red, orange, and yellow.
This increased scattering of blue and violet light is why the sky appears blue. Consequently, much of the blue and violet light is scattered away from our direct line of sight to the Sun. What remains and reaches our eyes directly is predominantly longer wavelengths, which combine to give the Sun a yellowish hue. This effect becomes more pronounced during sunrise and sunset. At these times, sunlight travels through a greater thickness of the atmosphere, leading to more scattering of blue and green light, allowing red and orange wavelengths to dominate.
How Star Color is Determined
A star’s color is directly linked to its surface temperature, a concept explained by blackbody radiation. Hotter objects emit light at shorter, higher-energy wavelengths, while cooler objects emit light at longer, lower-energy wavelengths. Hot stars appear blue or white, while cooler stars appear red or orange. For instance, stars around 10,000 Kelvin or more are blue, while those around 3,500 Kelvin appear red.
Our Sun is classified as a G2V star, indicating its spectral type and luminosity. The “G2” signifies a surface temperature of approximately 5,800 Kelvin, placing it in the yellow G class. The “V” denotes it is a main-sequence star, also known as a dwarf star. This classification helps astronomers understand its properties relative to other stars.