The night sky appears black, but this is a local illusion created by the vast emptiness between stars and galaxies. The blackness is simply the absence of light from distant sources hitting your eye, not the true, composite hue of all visible light in existence. If the light from every star, nebula, and galaxy were smeared across the sky, a single, uniform color would emerge.
Defining the Universe’s Average Color
The actual, average color of the observable universe is a pale, creamy beige, officially named “Cosmic Latte.” This hue is the result of combining the light from billions of stars and galaxies across the entire cosmos, representing the total optical output averaged over a specific volume of space. The specific color is a beige-white shade, close to an off-white, with a hex triplet value of approximately #FFF8E7.
This color is dominated by the light of older, yellower, and redder stars, which are far more numerous than the brilliant blue stars. Astronomers Karl Glazebrook and Ivan Baldry coined the term after correcting an initial calculation that had suggested a slightly greenish-white. The name “Cosmic Latte” was selected, fittingly nodding to the Italian word for milk, latteo, which also relates to the Milky Way galaxy.
The Scientific Method for Measurement
To determine this average color, astronomers calculated the “cosmic spectrum,” which is the total light energy emitted by a large sample of galaxies at every visible wavelength. The research team, led by Glazebrook and Baldry, analyzed the light spectra from over 200,000 galaxies using data from the 2dF Galaxy Redshift Survey.
Spectral analysis breaks down the light from each galaxy into its component wavelengths, much like a prism separates white light into a rainbow. By mathematically summing the brightness across all wavelengths, they created a single, representative spectrum showing the total power output of the universe at each color.
A crucial step was removing the effect of cosmological redshift, which stretches the light of receding galaxies toward the red end of the spectrum. Researchers de-redshifted the light before combining the data, ensuring the calculation reflected the light’s true emitted color, not its appearance due to the universe’s expansion. Finally, they converted this corrected cosmic spectrum into a single color that a standard human eye would perceive.
How the Color of the Universe Evolves
The universe’s current beige color is not static; it has changed dramatically over billions of years and will continue to evolve. When the universe was younger, it was a distinctly bluer color due to the prevalence of massive, hot, short-lived stars. These young, blue stars burned through their fuel rapidly, dominating the light output of early galaxies.
As the universe aged, the rate of star formation began to slow down, and those initial blue stars died off. The light became increasingly dominated by older, less massive stars, such as yellow sun-like stars and red dwarfs, which have much longer lifespans. This shift from hot blue stars to cooler, redder ones caused the average color to transition from blue to its current beige-white hue.
In the far future, the universe will become even redder as star formation ceases entirely and the longest-lived, low-mass red dwarf stars become the sole remaining light sources. Eventually, even these will fade, leaving the universe to become a cold, dark, and deep red place before all light is extinguished. The average color we observe today is a snapshot of this continuous aging process.