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"All-Star" -- The Discovery Files

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From their laboratories on a rocky planet dwarfed by the vastness of space, Clemson University scientists have managed to measure all of the starlight ever produced throughout the history of the observable universe. According to the new measurement, the number of photons (particles of visible light) that escaped into space after being emitted by stars translates to 4 times 10 to the 84th power, or 4 followed by 84 zeroes.

Credit: NSF/Karson Productions

Audio Transcript:

Full measure.

I'm Bob Karson with the Discovery Files, from the National Science Foundation.

(Sound effect: kids: "twinkle, twinkle, little star...") In the blackness of space, to us the stars seem to twinkle as we gaze at their light. So how much light have all the stars put out since they started showing up? A team led by Clemson University has, for the first time ever, measured the total amount of starlight emitted in the entire history of the observable universe.

You can think of light as particles called photons. The findings show since the first stars appeared until now, total number of photons emitted is -- (Sound effect: drumroll) are you ready? Four times ten to the eighty-fourth power! (Sound effect: bent cymbal crash) Wait! That looked bigger longhand; that'd be: (Sound effect: scrawling sounds) "total starlight in photons: four, comma" followed by 84 zeroes! Here's me with a post-it note. (Sound effect: crumple note)

Despite all those photons, the starlight that reaches us from outside our galaxy is exceedingly dim -- about like a 60-watt light bulb two-and-a-half miles away. The result of the universe being unimaginably large.

The researchers analyzed data collected by the Fermi Gamma-Ray Space Telescope to reconstruct and measure the cosmic fog, of all wavelengths of light that escape galaxies through time -- even the most distant ones. The team's ultimate goal: Find a way to look as far "back in the day" as the Big Bang. (Sound effect: cosmic explosion)

"The discovery files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at or on our podcast.

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