If you ask your friends or family members about the color of the sun, they are likely to give you a suspicious look and reply with a cocked eyebrow, “It’s yellow”. However, is it that simple? Is the color of the Sun really yellow?
Actually, it’s not. You’ve been hoodwinked since childhood into thinking that the Sun is yellow, while the real color of the Sun is actually white. The reason that the Sun generally looks yellow is because the Earth’s atmosphere scatters other colors like blue, green and violet more easily. On the other hand, colors like yellow, orange and red are less easily scattered, giving the Sun a yellowish appearance throughout the day and an orange/reddish tint when it is near the horizon.
There is a weird play of physics of light scattering that affect the color, and then the marginal effects of smoke, dust, and pollution, all of which contribute to making the Sun appear yellow most of the time.
Even when I first realized that the Sun was not yellow, I was still skeptical. To the naked eye, the Sun doesn’t appear to be a white burning star. However, to experience this white color of the Sun, you would need to transcend Earth’s atmosphere—perhaps in the International Space Station (ISS)!
How the Sun gets its color
The light emitted by the Sun that is visible to us is only a tiny part of the vast electromagnetic spectrum. This electromagnetic spectrum consists of a wide range of different waves, starting with smaller-than-atoms gamma rays to larger-than-Earth radio waves. Visible light in this electromagnetic spectrum lies somewhere in the middle and is only a tiny part of the full spectrum.
The entire range of visible light emitted by the Sun can best be seen through a prism. With a prism, you can break sunlight into its constituent colors—red, orange, yellow, green, blue, indigo and violet. These colors, from violet to red, are abbreviated as VIBGYOR (or ROYGBIV, in reverse). Violet has the lowest wavelength, while red has the highest wavelength. When all those colors are combined, it forms a white color, which is the net color of the Sun. Another way to experience the individual constituents of this net white sunlight is when there is a rainbow. You can then see a nice spectrum of the VIBGYOR colors of visible light.
How Earth’s atmosphere distorts the color of the sunlight
The reason that the Sun looks yellow to us is because of Earth’s atmosphere. As sunlight strikes atmospheric particles, it causes the electrons and protons to oscillate rapidly up and down, producing radiation of the same frequency as the incoming light, but sending it out in all directions. This process of redirecting sunlight is known as scattering. The Earth’s atmosphere scatters away light in the blue, indigo, and violet wavelength region more prominently, while higher wavelength colors like red, orange, and yellow are scattered sparsely. Due to this incongruous scattering, the Sun appears yellow. This is also why the sky appears blue during the day, as the blue wavelength is the most scattered color from the visible light spectrum.
When the Sun comes closer to Earth’s horizon, more of the blue light is scattered away by the atmosphere, which makes the Sun look more reddish at sunset and sunrise.
Color of the Sun in space
If you’re lucky and make it to the International Space Station someday, you can witness the actual white color of the Sun, because it won’t be distorted by our atmosphere. From outer space, the Sun will appear as a giant white shining ball.
Does the color of the Sun really matter?
Some of you may be wondering if the color of the Sun really makes any difference. Well, the color of the Sun is actually very important for astrophysicists. A technique called spectroscopy is used to split the spectrum of light coming from a given star. This is done because splitting can give clues about the characteristics of the star from which the light is emitted. It can help astronomers estimate if a star is made of heavier elements or lighter elements, which can determine its age and behavior patterns. Color also helps scientists estimate the temperature of a star. Contrary to intuition, cooler stars are actually more red in color. For example, Betelgeuse, which is a relatively cool star at about 3500oKelvin, is decidedly reddish in color. Hotter stars like Rigel, which are above 10,000o Kelvin, appear bluish. Our Sun is estimated to be approximately 5800oKelvin, and when viewed from outside Earth’s atmosphere, it appears white.
For eons, we lived with the notion that the color of the Sun is yellow. In fact, we are so accustomed to the idea of a yellow-colored Sun that astronomers often artificially alter the images of our white Sun to be more yellow in order to make it look more “natural”!
Now that you know all of this, the next time a teacher asks you to draw a picture of the Sun, draw it in white instead. When they ask why your Sun isn’t yellow, simply give her a quick lesson on our planet’s atmosphere, light, and the world around her!