‘Only a few objects in the Earth’s nighttime sky are bright enough to trigger our retina’s color-sensitive cones. The red planet Mars can do it. As does the blue supergiant star Rigel (Orion’s right kneecap) and the red supergiant Betelgeuse (Orion’s left armpit). But aside from these standouts, the pickings are slim. To the unaided eye, space is a dark and colorless place.
Not until you aim large telescopes does the universe show its true colors. Glowing objects, like stars, come in three basic colors: red, white, and blue–a cosmic face that would have pleased the founding fathers. Interstellar gas clouds can take on practically any color depending on how you photograph them, whereas a star’s color, follows directly from its surface temperature: Cool stars are red. Tepid stars are white. Hot stars are blue. Very hot stars are still blue. How about very, very hot places, like the 15-million-degree center of the Sun? Blue. To an astrophysicist, red-hot foods and red-hot lovers both leave room for improvement. It’s just that simple.
Or is it?
A conspiracy of astrophysical law and human physiology bars the existence of green stars. How about yellow stars? Some astronomy textbooks, many science-fiction stories, and nearly every person on the street, comprise the Sun-Is-Yellow movement. Professional photographers, however, would swear the Sun is blue; “daylight” film is color-balanced on the expectation that the light source (presumably the Sun) is strong in the blue. The old blue-dot flash cubes were just one example of the attempt to simulate the Sun’s blue light from indoor shots when using daylight film. Loft artists would argue, however, that the Sun is pure white, offering them the most accurate view of their selected paint pigments.
No doubt the Sun acquires a yellow-orange patina near the dusty horizon during sunrise and sunset. But at high noon, when atmospheric scattering is at a minimum, the color yellow does not spring to mind. Indeed, light sources that are truly yellow make white things look yellow. So if the Sun were pure yellow, then snow would look yellow–whether or not if fell near fire hydrants. ‘
-Neil DeGrasse Tyson
should kids start borrowing each others’ blue crayons to draw the sun now, or what?