Dear Community,
Over the years I have viewed many space telescope pictures of our universe. In these pictures, we see many different colors denoting planets, stars, pulsars, dwarfs etc.... Do these space telescopes capture the colors as they actually exist in real-time or is someone coloring in the colors after the picture is taken to denote the different astrological objects?
Thanks,
Techsent
More often than not, they don't. If the goal, however, is to present something to the public, then you will see a caption stating that these are "true color" images, or they are "natural color" images.
Often certain colors are assigned to certain emissions from a specific element like hydrogen. Oxygen III (double ionized) produces a natural green color. Hydrogen alpha is in the deep red. But most emissions are outside the tiny visible spectrum, so color assignment for the elements is done in the color processing in order to enhance what is happening in, say, a nebula. This gives scientists a better understanding of what is going on in the images they see.
Most images, fortunately, will state what the colors represent.
Another issue is saturation. When you look at, say, a nebula with a telescope you will rarely see any color. This is because the color cones in the retina aren't activated by dim light. When the Sun is setting, go outside and notice how the green leaves in trees become gray.
In dim light, the more than 100 million rods in your retina serve for our vision, but these are insensitive to color. Hence, gray is the result.
Looking through an 82" (McDonald), I did once see a very distinct blue ring in the Eskimo Nebula, or whatever they call it now. But this is rare.
Something I find unusual is that a larger telescope doesn't improve this. If you are looking at, say Mars, using a large telescope will capture more light, but it also enlarges the object. In fact, they balance so that surface brightness (brightness per unit area) never increases, though total brightness does with increasing aperture.
So, even when you do see color, it is impossible for the human eye to see these beautiful images even if you have a giant telescope.
My pet project of years ago was why the Sun was treated as if it is a yellow star. It is demonstrably not a yellow star since noon time images (projections -- see my avatar) of it are white, and it is blue light that scatters away from sunlight as it passes through our atmosphere, hence it must be blue light that would need to be added into the white noontime projection, and you can't get a yellow anything when blue is added to white.
The Sun is a great example of how celestial objects are handled when it comes to color. There isn't much appeal of a plain, though bright, white sun, so expect to keep seeing a range of color for it.
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