- Although the Sun appears yellow or orange, it is actually brilliant white.
- Because of the Earth’s atmosphere, Sun looks yellow and changes colors at sunrise and sunset.
- The actual color of the Sun can be viewed from space because there are no atmospheric molecules for light to interact with.
Our Sun is a nearly perfect sphere of hot plasma located at the center of the Solar System. It is a G-type main-sequence star that accounts for more than 99.8% of the mass of the Solar System.
It is by far the major source of energy for life on Earth. However, most people don’t know the very basic property of the Sun; what color is it?
If you ask a bunch of people to tell you what is the color of our Sun, chances are they will look at you like you are a fool and tell you the obvious answer: it’s yellow.
But is it really?
You will be surprised to know that the Sun is not red or orange or yellow. Instead, the Sun is all colors fused together, which appear to our eyes as white.
Rainbow light — a form of a multicolored circular arc — comes from the Sun, and is split into seven colors. Every color possesses a unique wavelength. Blue has the shortest, and red has the longest wavelength.
Why Does The Sun Look Yellow or Orange?
From our perspective, the Sun does look yellow/orange, especially shortly after sunrise and before sunset. This happens due to the Earth’s atmosphere.
The Sun emits a wide range of frequencies of light. At the top of the Earth’s atmosphere, sunlight is comprised of nearly 50% infrared light, 40% visible light, and 10% ultraviolet light. The atmosphere filters out more than 70% of solar ultraviolet, particularly at the shortest wavelengths.
Photons in the lower end of the spectrum (yellow, orange, red) are less easily scattered, while the higher end of the spectrum (violet, indigo, and blue) are more likely to be scattered away.
It has also been observed that the Sun emits more photons in the green segment of the spectrum than any other.
At noon, the shorter waves (blue light) strike air molecules in the upper atmosphere and get scattered multiple times before reaching our eyes. This scattering effect is also what gives the sky its blue appearance.
Closer to the horizon, Sun appears orange
However, at sunrise and sunset, the Sun is closer to the horizon, which means light passes through more atmospheric molecules. With more atmosphere, blue photons are scattered even more, leaving only the low-energy yellow, red, and orange light.
And when there are dust and smoke in the air, it enhances the scattering effect, giving Sun a more reddish appearance.
The Actual Color Of Our Sun
If you view the Sun from the Moon or the International Space Station (ISS), you will see its true color. Since there is no atmosphere in space, light has nothing to interact with. Therefore, the Sun appears brilliant white from space, with a CIE color-space index of (0.3, 0.3).
Image of the Sun taken from ISS | NASA
The color also indicates the temperature of the star. Our Sun, for example, has a surface temperature of about 5,505°C and an average luminance of about 1.88 giga candela per square meter.
Cooler stars appear redder than others. Betelgeuse, one of the brightest stars in the night sky, has swelled and cooled to become a red supergiant. Its temperature ranges between 3,000°C and 3,400°C.
Hotter stars look blue. Riggle, for example, appears as a single blue-white star to the naked eye, and it can get above 11,000°C.
False Color Images
If our Sun is actually white and its visible output peaks in the green, then why are some solar images blue, or green, or orange, or red?
Actually, human eyes can detect only a small segment of the electromagnetic spectrum, and this segment is called visible light. Ultraviolet and infrared rays have shorter and longer wavelengths than visible light, respectively.
Image of the Sun captured in extreme ultraviolet | Credit: NASA
Astronomical instruments, such as Solar and Heliospheric Observatory, capture Sun’s data in ultraviolet and infrared rays. The images obtained from such data must be colored so that our eyes can see them. Thus, scientists use unique colors (like neon green or bright red) to present non-seeable versions of the Sun.
To make pictures more like something people would expect, scientists often color actual images of the Sun captured in visible white light.
Sun captured in visible white light and then color coded to make it look orange | Credit: NASA / ESA
Sometimes, the Sun’s display color is culturally determined. A kindergartener in the United States, for example, often colors the Sun yellow. Whereas, a Japanese kindergartener usually colors it orange.
Despite these differences, our Sun actually is bright white.