With a lot of space photography the color is added of enhanced after the photo is taken. So some of the photos are an artists conception backed up
With many objects and phenomena in space, color is only made visible by the power of a telescope. Planetary nebulae provide a good example. These
bizarre and detailed structures -- often symmetrical bubbles or hourglass shapes -- are the result of gas that's been cast into space by a dying
star. Different gases, such as oxygen, hydrogen and nitrogen, each generate a different wavelength, or color, depending on the local physical
Human eyes, even if very near to or inside one of these nebulae, could not make out the colors, however, because the emissions are too faint. They
would see little more than a big gray area.
Hubble astronomers make multiple long exposures to draw out these colors. They also employ a different filter for each exposure to block all but a
certain color of light. A digital imager records a grayscale image. After adding the color in Photoshop (and also eliminating artifacts generated by
piecing the data together) the filtered images are combined.
In some cases, the colors are as true to reality as anyone could imagine. Other times, as with the Eagle Nebula, colors are changed for effect
Hydrogen and sulfur were each detected in red tones, so the hydrogen, which involved a shorter wavelength, was made green.
When images are taken outside the visible light spectrum -- in the infrared, for example -- the color choices are entirely up to the astronomers and
"This is a representation of some kind to convey the information that Hubble has gathered," Brecher says. "It's scientifically sound, but their
presentation is subjective."
Levay says the process of coloring photos is never arbitrary.
"What we're doing is representing physical processes and representing actual astronomical observations in a visual and artistic way," Levay
explained shortly after discussing the issue with Brecher. "I'm adding value, but it's not arbitrarily added. What I'm mostly doing is enhancing
what's already there."