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Why Aren’t There Any Green Stars
Going outside at night in clear weather and looking at the sky, you can see stars of various colors - from reddish to bluish. But there is not a single green star. Where does this injustice come from? Let's try to figure it out.
The stars cannot boast of a variety of colors. The main reason is the structure of our eyes. We have only three types of light-sensitive cones - blue, red, and green, and for our eye to see any color, the other two need to be much smaller.
Stars emit in a very wide range, and the green color is in the very middle of the spectrum and therefore merging with the rest of the colors reaches us in the form of white. The rest of the colors are combinations of these three: for example, if we look at a lemon, then the cones that perceive the red and green colors are activated, the blue ones are inactive, and the brain interprets the general color as yellow; if green and blue cones are activated, the brain sees an aqua color; red and blue are activated - magenta.
If you take a steel bar and start heating, it will begin to change color with increasing temperature. At first, it will glow red, then orange, then blue and white. Then it will melt. Why is it glowing? Any substance above absolute zero (about -273 ° C) emits light. The measure of light and its frequency relies on the temperature. The warmer the object, the shorter the wavelength. Changing the temperature of a star will turn it orange, yellow, red, or blue, but you can't make it green. Our eyes just won't see her like that.
Purple is another shade you don't find in the night sky. This is because that our eyes see blue better compared to violet, and stars that emit violet light additionally produce a ton of blue light.