"That's why we built the Hubble Space Telescope, because we can't see these things," says Zoltan Levay, who leads a team of imaging specialists at the Space Telescope Science Institute (STScI), which operates Hubble and prepares most of the photographs.

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."

Levay points out that color is in fact a quantitative thing, a numerical difference between brightness measurements in well-defined wavelength bands, "though it may not have much relationship to perceived color." He says the measured color of Betelgeuse, the red giant, is redder than many other stars, even though the physiology of the eye may prevent us from actually perceiving the subtleties.

What does this have to do with those beautiful Hubble pictures?

"That's precisely what we're doing," he said. "Now, we're going a step further. We're twiddling the knobs on the TV screen. We may be turning up the color knob a little bit or playing with the brightness."

Levay and his colleagues sometimes take the editing process another step. Images made with Hubble's infrared camera, called NICMOS, have no intrinsic color values in the visible spectrum. To these photos, the image specialists typically apply a corresponding range of colors from the visible realm in a logical pattern -- red for longer wavelengths and blue for shorter.

"Color is a somewhat fuzzy term," Levay admits in relation to the infrared pictures. "We are artificially applying a perceptual color to light that we cannot perceive." One astronomer would not necessarily apply the same colors to a given infrared image as another, he said, but the same logic with respect to wavelength shifts is typically employed.

Levay points out that what he does is nothing more than an extension of two manipulation techniques that transformed modern astronomy.

"We've been manipulating our view of the universe since the advent of black-and-white photography," he said. "And even before. A telescope manipulates your view of the universe, because it expands the size of your eyes."

Manipulation, of course, opens the door to misrepresentation.

"You can definitely mislead," Levay said. "Mistakes get made. Science happens by mistakes being made. But those mistakes are corrected."

Back in the Voyager days, some critics objected to what they saw as excessive goosing of color to bring out subtle details.

"In certain specific cases, the colors were stretched strongly to emphasize particular information," Levay says. "By and large, Voyager produced wonderful, evocative, and mostly quite color-accurate images."

Today, there is small group who criticizes what Levay and his colleagues do with Hubble pictures, according to Ray Villard, news director at the STScI and a man who helps choose which Hubble images the world will see. Villard thinks some of the criticism is rooted in envy over Hubble's wide popularity, or suspicion that something in the sky is being hidden from the public, or that mundane-looking data is heavily glamorized purely for publicity.

Villard dismisses these suggestions. He also notes, based on his decade of experience in answering public questions about the telescope, that the vast majority of people "don't really care" how the photos are processed. "They don't think about it, any more than one would worry if a beautiful Kodachrome photo of a sunset was really the exact color."

The STScI's guiding principle, Villard says, is to create aesthetically beautiful pictures that yield a lot of science. "An aesthetic picture also conveys the maximum amount of information. Because the Hubble images are intrinsically very evocative, it's not a crime to artistically bring out their most attractive features."

The interpretation of color has gone awry before at the STScI, grossly in one example from the orbiting observatory's earliest days. The public, however, never saw it.

The offending photo was of Jupiter. Going by the numbers, an astronomer presented Villard with a picture of a green gas giant. Knowing they would be laughed at by every amateur astronomer who had ever spied the planet's pale reds and creams through a backyard telescope, Villard protested.

"That's what it is," the astronomer retorted, sticking to his data.

Eventually, Villard persuaded the astronomer that the public should not see a green Jupiter, no matter what data might be behind the picture. He later learned a lesson in just how subjective color can be: "Come to find out," Villard recalls, "the astronomer was color blind."