Monday, July 5, 2021

Is the sun yellow?

Young minds usually color the Sun yellow or orange, or even red. Have you ever thought about what color the Sun actually is? How do you think you could find out what color the Sun really is (without look at it directly)? Below is an exploration for you to try.

It is a common misconception that the Sun is yellow, or orange or even red. However, the Sun is essentially all colors mixed together, which appear to our eyes as white. 

This is easy to see in pictures taken from space.   Rainbows are light from the Sun, separated into its colors. Each color in the rainbow (red, orange, yellow, green, blue, violet) has a different wavelength. Red is the longest, blue the shortest.

  When we see the Sun at sunrise or sunset, when it is low in the sky, it may appear yellow, orange, or red. But that is only because its short-wavelength colors (green, blue, violet) are scattered out by the Earth's atmosphere, much like small waves are dispersed by big rocks along the shore. Hence only the reds, yellows, and oranges get through the thick atmosphere to our eyes.

When the Sun is high in the sky, the shorter waves, primarily the blue, strike air molecues in the upper atmosphere and bounce around and scatter. Hence explaining why the sky looks blue.

Some people think that enough blue light is scattered out in the Earth's atmosphere to cause the Sun to appear slightly yellow. 

𝐖𝐡𝐚𝐭 𝐝𝐨 𝐲𝐨𝐮 𝐭𝐡𝐢𝐧𝐤?

Some think that the Sun's output in visible light peaks in the yellow. However, the Sun's visible output peaks in the green:

So why are the solar images sometimes green, or blue, or red, or orange? View current images of the Sun

Actually, all forms of light and energy are part of the same phenomena: the electromagnetic spectrum. Our eyes can detect only a small amount of this energy, that portion we call "visible light." Radio waves, X-rays, microwaves, gamma rays, and the rest all have longer or shorter wavelengths than visible light, but otherwise are the same phenomena.

Scientific instruments can sometimes detect light that our eyes cannot. When people want to look at those, say, X-ray or ultraviolet images, they need to color them something that our eyes can detect. So the scientists pick some bright color, a color that would never be confused with viewing the Sun in white light. That way, we know from seeing a picture of a neon green or bright red Sun that the image was actually taken in some non-seeable version of light such as extreme ultraviolet or X-rays.

It is hard for many people, even scientists, to admit that the Sun they are so used to living with is actually white. So sometimes they even color pictures of the Sun taken in visible or "white" light to look more like something we would expect. We have included a picture of the Sun taken in visible white light, but which the scientists have processed to make it appear orange, for our benefit!

Sometimes the display color of the Sun is culturally determined. If a kindergartener in the USA colors a picture of the Sun, they will usually make it yellow. However, a kindergartener in Japan would normally color it red!


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