WASHINGTON (AP) -- When Mother Nature decorated the universe, she chose a color slightly greener than a pale, pale turquoise. And like an ordinary human homeowner, she'll redecorate eventually, shifting to a more reddish hue.
Astronomers at Johns Hopkins University said that averaging all the colors from the light of 200,000 galaxies shows that the current color of the universe is a sprightly green. They predict the color will shift toward red, however, in a few billion years.
The current color "is quite close to the standard shade of pale turquoise, although it's a few percent greener," said Karl Glazebrook, who worked out the color scheme with another Hopkins researcher, Ivan Baldry. They presented their findings Thursday at the national meeting of the American Astronomical Society.
By visual perception, the average color found by the astronomers is between the standard colors of medium aquamarine and pale turquoise.
"We haven't been to a paint shop yet to see if there is a fancy name for it," said Baldry. He calls the color "cosmic spectrum green."
To find this average color, the astronomers gathered light from galaxies out to several billion light years. They ran the light through instruments that broke it into various colors, sort of like a prism can turn sunlight into a rainbow. They then averaged the color values for all the light and converted it to the primary color scale seen by the human eye.
The astronomers also converted the color to the red-green-blue values used by computer buffs to describe colors. The computer RGB scale numbers for cosmic spectrum green are 0.269, 0.388 and 0.342.
Baldry said that cosmic spectrum green could be seen in the heavens by the human eye only if all the light was viewed at once and the stars were not moving -- a clear impossibility.
To determine the average color, Baldry said the researchers adjusted for what is called the red shift. All stars in the universe are separating from each other and this motion skews the colors toward red. The cosmic spectrum green is adjusted for this motion.
Baldry said converting the color spectrum detected by their instruments to the color detected by the human eye was a "whimsical intellectual exercise" and he joked about making T-shirts and coffee mugs using the cosmic green.
But the work did have a serious purpose.
The astronomers were analyzing the colors from the 200,000 galaxies to determine the relative ages of the stars within those galaxies. Young stars are hot and blue; middle aged stars are more green, and stars nearing their end tend to be redder.
Earlier in the 14 or 15 billion-year life of the universe, said Baldry, the average color of the universe was more blue because it had a higher proportion of young stars. The formation of new stars has decreased for billions of years and the ratio of young-to-old stars has changed, giving the universe the current average hue of green.
Eventually, billions of years in the future, said Baldry, the average color will trend toward red as the star population ages further and even fewer young stars are formed.
