Astronomers have measured all the starlight ever emitted

The tally counts up the stray photons roaming through space

illustration of galaxies emitting gamma rays

THROUGH THE DARKNESS  Gamma rays bursting from distant galaxies, like the one shown in the center of this artist’s illustration, can illuminate the diffuse light, called extragalactic background light, that manages escape its dusty environs.

Aurore Simonnet/Swift/NASA

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