"Galaxy Blue" by Souricette-du-13 / CC BY-SA 4.0

Here’s How Much Starlight Has Been Created Since the Beginning of the Universe

Nov 30, 2018

By Yasemin Saplakoglu

Hidden in the darkness among the stars is all the light that the universe has created since the Big Bang.

Now, scientists think they know approximately how much light that is. Since their birth a couple million years after the Big Bang, stars have produced around 4 x 10^84 photons, or particles of light, according to new measurements reported today (Nov. 29) in the journal Science.

Most of the light in the universe comes from stars, said Marco Ajello, study co-author and an astrophysicist at Clemson University.

Here’s what happens: Stars like our sun are powered by nuclear reactions in the core, where hydrogen protons are fused together to create helium. This process also releases energy in the form of gamma-ray photons. These photons have a hundred million times more energy than the ordinary photons we see as visible light.

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