The sun isn’t the only light source behind that summer tan | Science News

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The sun isn’t the only light source behind that summer tan

Tiny amount of ultraviolet light comes from the Big Bang and other stars, galaxies

By
2:30pm, September 20, 2016
Milky Way Galaxy

CATCHING SOME GALACTIC RAYS Galaxies, such as those in this image from the Paranal Observatory in Chile, are responsible for less than one-billionth of 1 percent of your suntan. The bright blue-white points of light in this picture are stars in the Milky Way; most other objects are galaxies.

Your summer suntan is almost entirely locally sourced. But a smidgen of that healthy glow hails not from the sun but from the ultraviolet light of nearby stars and other galaxies: less than one-billionth of 1 percent. Even photons lingering from the Big Bang contribute some: roughly 0.001 percent.

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