A measurement of all the starlight ever produced

earthsky.org | 12/5/2018 | Eleanor Imster
Click For Photo: https://en.es-static.us/upl/2016/12/Ultra-Deep-Survey-image-cp-300x169.jpg

An international team of scientists says it has measured all of the starlight ever produced throughout the 13.7-billion-year history of the observable universe. Sounds wild, right? But the new study was published November 30, 2018 in the peer-reviewed journal Science. According to the new measurement, the number of photons (particles of visible light) that have escaped into space since the universe began – after being emitted by stars – translates to 4×1084.

That’s 4,000,000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000 photons of light.

Clemson - College - Science - Astrophysicist - Marco

Clemson College of Science astrophysicist Marco Ajello – who is featured in the video above – is lead author of the new paper. He said in a statement:

… we were able to measure the entire amount of starlight ever emitted. This has never been done before.

Course - Variables - Number - Figure - Scientists

And, of course, there are many variables, so this number is just a ballpark figure. Still, it’s impressive. How did scientists arrive at this number?

EarthSky lunar calendars are cool! They make great gifts. Order now. Going fast!

Part - Hubble - Ultra - Deep - Field

This is part of the Hubble Ultra Deep Field. It shows some of the oldest starlight ever seen in our universe. Image via NASA/ ESA.

Astrophysicists believe that our universe started in a Big Bang, some 13.7 billion years ago. They think it started forming stars very quickly after its birth, when it was only a few hundred million years old. Since then, the universe has become a star-making tour de force.

Universe - Today - Galaxies - Trillion-trillion - Stars

In the universe today, there are about two trillion galaxies and about a trillion-trillion stars.

Measuring all of the starlight in this vast universe is clearly a daunting task. This team of scientists says it did it by analyzing data from NASA’s Fermi Gamma-ray Space Telescope.

Calculations - Measurements - Background - Light - EBL

The new calculations are based on measurements of the extragalactic background light, also known as the EBL. You can think of the EBL as a cosmic fog composed of...
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