Repainting the cosmic palette

After all the hue and cry about the color of the universe, astronomers have now revised their findings. It’s not pale green but boring old beige.

In a whimsical calculation that received wide publicity last January, Karl Glazebrook and Ivan K. Baldry of the Johns Hopkins University in Baltimore estimated the average color of the cosmos: the hue that the human eye would perceive if all the light from nearby galaxies was blended into a single point of light (SN: 1/26/02, p. 62: Seeing green: Color of the cosmos).

The astronomers base both their original and revised calculations on the colors of some 200,000 galaxies recorded in the largest galaxy survey completed to date. The number and distribution of galaxies in the mammoth survey, based in Australia and known as 2dF or 2-degree field, provide a representative sample of the local universe, Glazebrook and Baldry note.

The researchers initially announced that if an observer could peer down on our universe, the combined colors from all the visible galaxies would register to the eye as pale green. But when Mark D. Fairchild, director of the Munsell Color Science Laboratory at the Rochester Institute of Technology in New York took a closer look at the astronomers’ finding, he found a flaw.

Fairchild and his colleagues discovered that the software the Hopkins astronomers used to analyze galaxy colors incorrectly set the white point, the color that the eye sees as white under varying conditions of illumination. That error caused the color green to appear more prominent in the astronomers’ analysis than it actually is.

“It’s our fault for not taking the color science seriously enough,” adds Glazebrook, who has posted a revised version of his analysis online (http://www.pha.jhu.edu/~kgb/cosspec).