The colour of the cosmos

What you get from mixing the cosmic colour spectrum

The Universe is turquoise, say astronomers in the United States.

The hue, somewhere between pale turquoise and medium aquamarine, is what you would get from mixing all the visible light in the cosmos.

We haven't actually been to a paint shop yet to see if they have any fancy names for this colour

Ivan Baldry, Johns Hopkins University

The astronomers behind the discovery, Ivan Baldry and Karl Glazebrook, have called the colour cosmic spectrum green. But they say there is no way you would actually see it from Earth.

Dr Baldry, of Johns Hopkins University in Baltimore, Maryland, said: "The only way to see it is if you saw all the Universe from the same distance away and it was not moving."

Blue period

The turquoise colour is in the middle of a cosmic spectrum created by the researchers.

It shows the Universe beginning with a blue period, due to the large number of young, hot stars.

The glowing remains of a dying star

The colour will eventually change to red, as older stars become red giants and fewer new ones are born.

"The reason the colour's changing is because the rate of stars forming is changing," Dr Baldry told reporters at this week's American Astronomical Society meeting in Washington DC.

"We're in a stage of a declining rate of star formation. More stars were forming in the past than at the present time."

Star birth boom

The discovery was a by-product of research to find the rate of star birth as the Universe aged. The scientists looked at more than 200,000 galaxies between two and three billion light-years from Earth.

A light-year, the distance light travels in a year, is about 10 trillion kilometres (6 trillion miles).

"This colour's a whimsical intellectual exercise, but the star formation history is astronomical research," Dr Baldry said.

The researchers joke that the colour seems suitable for home decorating or T-shirts.

Dr Baldry added: "We haven't actually been to a paint shop yet to see if they have any fancy names for this colour."