¡SkyCaramba! Weekly astronomy blog for the week ending August 15, 2015
Stars come in several colors. Antares is red. Aldebaran and Arcturus are orange. Pollux is yellow. Sirius is blue. There aren’t any green stars. Why did nature skip that color when covering everything else in the spectrum from red to blue? Well, it didn’t. It just looks that way.
Stars are incandescent. That means the light they emit is the result of heat. One property of incandescent light is that it is created in a continuum of wavelengths. When you let white sunlight shine through a prism, you see a continuum of colors called a spectrum. White light is actually made of all those colors. If you still have an incandescent light bulb, you can see the same spectrum.
If you put a colored filter between your eyes and an incandescent light source, you let some wavelengths pass through more than others. The wavelengths that pass through most easily determine the color you see. That’s how a white light could be made to appear red, yellow, or green in incandescent traffic signals. It’s also how stained glass artisans make portraits in light of all colors.
Colored filters don’t actually ...