True color of the cosmos revealed, pale green

Pale turquoise or mint chocolate chip?

By Richard Stenger
CNN.com Sci-Tech

(CNN) -- What would one see if the rainbow of lights that comprise the visible universe were mixed together into one color? Astronomers think something slightly greener than pale turquoise.

Lest one dismiss the matter as trivial, consider that the blend could help shed light on the ultimate fate of the cosmos.

Johns Hopkins University researchers converted the visible color wavelengths into a spectrum, much like sunlight when it breaks down into the colors of a rainbow. Then, taking into account the varying concentrations of different visible light wavelengths, they converted the spectrum into the one color that the eye would see.

And what is the true hue of the cosmic stew?

"The color is quite close to the standard shade of pale turquoise," said Karl Glazebrook, who with colleague Ivan Baldry presented the findings to the American Astronomical Society this week.

"This would be what we'd get if we took all the light in the universe and passed it through a prism," Baldry said in a statement.

Do others agree with their assessment?

"I'd call that mint green. It's the color of mint chocolate chip ice cream," said one viewer.

A spectral slice of the universe, before the colors are blended into one

Glazebrook and Baldry joke about pitching t-shirts and coffee mugs emblazoned with "the true color of the universe." But their research stems from rather sober investigations into theories about the history and future of stars.

To come up with the chromatic signature of the cosmos, the two analyzed a celestial census of the light from more than 200,000 galaxies.

"We believe that the survey is large enough, reaching out several billion light years, to make this a truly representative sample," Baldry said. There is one caveat. The shade is arbitrary. The level of brightness could range from dark to light.

The color itself might seem surprising since there are no green stars, Glazebrook acknowledged. The hue, however, reflects the preponderance of the most common kinds of stars, old red ones and young blue ones. A combination of light from the two sources produces green.

The color composite was created during an analysis of different theories about star formation. Scientists think that the universe first went through a "blue phase," populated mostly by young stars; then shifted into its current "green phase," with its mixture of young and old; and will eventually experience a "red phase," when it possesses mostly aging red giants.