Cast your mind back to when you were a little kid and you would scribble a yellow Sun in the corner of each of your drawings. Or how about in high school when you’d flick through your science textbook and see the sun printed as an orangey-yellow and red ball of light.
Well, it seems like such a stupid question to ask what color the Sun is, especially when we look up to the sky and it appears as a yellowy-orange. However, have you ever actually wondered what color the Sun actually is, without looking directly at it?
It seems that there are many correct and different answers to this seemingly simple question. In this article we’re going to look at some of these answers, and why the Sun appears as certain colors during different times of the day.
Let’s get started!
What Is The Actual Color Of The Sun?
As humans, our perception of color is influenced by both the wavelength and intensity of the emitted light, as well as the limitations of our eyesight, environmental factors, and our brains.
To determine the color of a star, both the surface temperature and the wavelength that the human eye can perceive will come into play.
The Sun emits light over a variety of wavelengths (otherwise known as colors). Apart from gamma rays, the Sun emits light across all parts of the electromagnetic spectrum.
As with all matter, the Sun emits a “black body spectrum”, which is defined by its surface temperature. For the Sun, this black body spectrum is a bell-shaped curve that involves electromagnetic (EM) radiation at various different wavelengths, from long infrared to short ultraviolet.
When there are extremely explosive and high-energy solar flare events, the Sun emits an extremely large amount of x-ray and gamma-ray radiation. These solar flares are a result of a sudden release of magnetic field energy which accelerates charged particle plasmas.
This all sounds a little confusing, but what it does show is that the Sun emits energy at all wavelengths, which means that it can produce all colors across the spectrum.
However, the Sun emits most of its energy around 500 nm, which is close to green-blue light. This means that some people would actually classify the Sun as blue-green.
This is because the Sun’s radiation frequency is governed by its surface temperature – which is around 5,780 Kelvin.
A higher surface temperature would have a shorter maximum wavelength, which means that the Sun would peak in the blue or violet (or even the ultra-violet) part of the spectrum.
If the Sun had a lower surface temperature, then its spectrum would peak in the yellow, orange, or even red part. So, by that logic, cooler stars appear to be red, and hotter stars appear blue. Orange, yellow, and white stars have a surface temperature somewhere in between.
However, this is physics and not perception. The human eye doesn’t perceive light by averaging the various colors of the spectrum together. Therefore, a very slight green light doesn’t look green to the human eye, which makes the Sun look white.
For our eyes to be able to perceive the Sun as green, it needs to emit only green light.
Why Does the Sun Look Yellow?
As we’ve established, where the Sun’s energy emits on the spectrum is closest to the green-blue color. However, the human eye perceives the Sun as white, which is pretty confusing when we generally see the Sun as yellow.
This is to do with the Earth’s atmosphere, as it scatters blue light more efficiently than red light. As there is a slight deficit in blue light, it means that the human eye perceives the color of the Sun as yellow.
The more of Earth’s atmosphere that the Sun’s light passes through, the more that blue light is scattered. So, during both sunrise and sunset, there is a far greater chance of red light being in the Sun’s spectrum, which is why it looks yellow or orange.
The Electromagnetic Spectrum
Have you ever shone a light through a prism to create an artificial rainbow? Well, when solar light is directed through a prism, a beam of light comes out of the other end which shows the various color components in their purest form.
This is part of the electromagnetic spectrum, and it’s how we can see all the colors that are visible to the naked eye.
By this logic, the Sun is considered to be white, as there is no single color frequency that is consistently brighter than the others. Each of the visible colors is present in the sunlight in equal amounts. However, most solar images of the sun are often green, blue, red, and orange.
If we were to speak critically, however, these color frequencies aren’t present in the exact same amount, it’s just that the variances aren’t significant enough to be meaningful. Therefore it is much more accurate to say that the Sun is white, rather than saying it’s one singular, pure color.
As our eyes can only detect a small amount of energy known as “visible light”, X-rays, radio waves, microwaves, and gamma rays cannot be detected by the naked human eye. However, scientific instruments can sometimes detect light that our eyes are unable to.
So, scientists often pick a bright color – a color that would never be confused with viewing the sun in white light – to color an image of the Sun. If you see a picture of bright red or neon green Sun, the image may actually have been taken in a non-seeable version of light, such as X-ray or extreme ultraviolet.
Similarly, scientists often color pictures of the Sun in visible or white light as something we would expect to see. Often pictures of the Sun are colored orange for our own benefit.
Despite these changes, the Sun is actually white in color.
What Color Is The Sunset On Different Planets?
Although it’s common to see a peachy sky or fiery rose inferno during sunset on Earth, sunset colors aren’t uniform across our solar system. This is due in large part to the atmosphere of each planet, and how particles in the atmosphere scatter light.
So, the answer varies depending on which planet you are looking at.
On Mars, for instance, the Sun comes and goes with a blue glow, whereas, on Uranus, the sky transitions from blue to turquoise during sunset.
On Earth, blue light is scattered more efficiently, so when the Sun sets, it often appears in hues of yellow, orange, and red.
So, there you have it, everything you need to know about the color of the Sun. It’s certainly interesting to think that our perception of the Sun is based heavily on what light can be perceived by the human eye.
It is also interesting that due to the surface temperature of the Sun, its wavelength is closest to blue-green, however, we understand the Sun to be white based on the fact that it emits light across the whole of the electromagnetic spectrum.
What is also fascinating is that the way light is scattered in our atmosphere has an effect on the color in which the Sun appears in the sky, giving it that orangey-yellow glow, particularly at sunrise and sunset.
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