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04 декабря 2018, 02:53

We Now Know How Bright the Universe Is

Nothing is impossible. Just ask the researchers who managed to quantify all of the starlight ever produced throughout the history of the observable universe.

Clemson University scientists analyzed data from NASA’s Fermi Gamma-ray Space Telescope to determine the history of star formation over most of the universe’s lifetime.

Our universe began forming the first stars after only a few hundred million years.

Now some 13.7 billion years old, it boasts two trillion galaxies and a trillion-trillion stars—all of which Clemson College of Science astrophysicist Marco Ajello and his team measure.

“This has never been done before,” lead study author Ajello said in a statement. “Most of this light is emitted by stars that live in galaxies. And, so, this has allowed us to better understand the stellar-evolution process and gain captivating insights into how the universe produced its luminous content.”

Putting a number on the amount of starlight ever produced is like trying to sneeze with your eyes open—it’s difficult, a bit painful, and not recommended.

That didn’t stop the Clemson researchers, though.

According to their new measurement, the volume of photons (particles of visible light) that escaped into space after being emitted by stars translates to 40^84.

Which, in layman’s terms, equals 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.

Despite that mind-blowingly colossal number, much of the starlight actually reaching Earth (from sources outside our galaxy) is “exceedingly dim,” according to the University. Think of it like a 60-watt light bulb, viewed in complete darkness—from about 2.5 miles away.

The Fermi Gamma-ray Space Telescope (FGST) launched into low Earth orbit more than a decade ago.

Ajello and postdoc fellow Vaidehi Paliya analyzed nearly nine years of its data concerning gamma-ray signals from 739 blazars—galaxies containing supermassive black holes able to release jets of energetic particles that streak across the cosmos at nearly the speed of light.

“By using blazars at different distances from us … we measured the total starlight of each epoch—one billion years ago, two billion years ago, six billion years ago, etc.—all the way back to when stars were first formed,” Paliya said. “This allowed us to … determine the star-formation history of the universe in a more effective manner than had been achieved before.”

The results and ramifications of the new measurement process are detailed in a paper published last week by the journal Science.

More coverage on Geek.com:

Source: https://www.geek.com/news/we-now-know-how-bright-the-universe-is-1763848/?source=news