I was checking out this picture of the Andromeda Galaxy and in the caption you can find “This image was taken with an hydrogen-alpha filter”: what is it? Thanks!
In: Physics
Thanks u/Snakeinbeaver, I’ll just go and to try to ELI5.
You know how when metal goes really hot it glows red? That’s because everything that has heat gives off light, all the time. But the ‘color’ of the light is related to the temperature of the object, and human eyes can only see light produced by things that are thousands of degrees in temperature because our human eyes can see only certain colors.
I said the ‘color’ was based on the temperature *but* it’s also based on the elements that are in the hot material. So all together, this is why stars that contain a lot of hydrogen, and are really, really hot, are all that kind of whitish/orangish/yellow. That color comes from a mix of the hot-star-temperature AND the hydrogen the star is made from.
Now, that whitish/orangish/yellow color is actually what our eyes see from a bunch of different different individuals all on top of each other, like using half a box of crayons to draw the same Sun on top of itself in a picture. It’s chaotic and confusing. So you can use a special filter, called a “hydrogen-alpha” filter that removes 99% of the different colors and leaves you with a single reddish-orange color, a sun drawn from a single burnt-sienna crayon. It’s much easier to see and understand just this one color vs. all those crayons all stacked up on top of each other.
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