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Astronomers follow the story of the star formation of the universe | astronomy



Astronomers believe that our universe formed the first stars several hundred million years ago. Since then, the universe has become a star-making tour . There are now about two trillion galaxies and one trillion trillion stars. Using new methods of measuring starlight, astronomers analyzed data from NASA's Fermi Gamma-Ray Space Telescope to determine the history of star formation throughout the lifetime of the universe.

  This map of the entire sky shows the position of 739 blazars used in NASA Fermi Gamma-ray Space Telescope Measurement of extragalactic background light. The background shows the sky as it appears in gamma rays with energies in excess of 1<div class="e3lan e3lan-in-post1"><script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
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</script></div>0 billion electron volts created from nine years of observations from Fermi's Large Area Telescope. The plane of our Milky Way runs along the middle of the plot. Picture credits: Cooperation between NASA, DOE and Fermi LAT.

This all-sky map shows the location of 739 blazars used in NASA's Fermi-Gamma-Ray Space Telescope Survey for the extragalactic background light. The background shows the sky as it appears in gamma rays with energies in excess of 10 billion electron volts created from nine years of observations from Fermi's Large Area Telescope. The plane of our Milky Way runs along the middle of the plot. Picture credits: Cooperation between NASA, DOE and Fermi LAT.

One of the main goals of the Fermi mission was to evaluate the extragalactic backlight (EBL), a cosmic nebula that consists of all the ultraviolet, visible, and infrared light stars about the history of the universe.

"With the data collected by the Fermi telescope, we were able to measure the total amount of starlight that was ever emitted," Dr. Marco Ajello, astrophysicist at Clemson University. "

" Light is emitted by stars that live in galaxies. In this way we could better understand the process of stellar evolution and gain fascinating insights into how the universe has produced its luminous content. "

Dr. Ajello and co-authors analyzed data on gamma ray signals from 739 blazars for almost nine years.

"Blazars are galaxies with supermassive black holes that are capable of releasing tightly collimated beams of high-energy particles that jump out of their galaxies at almost the speed of light through the cosmos," they explained.

"If any of these Jets is aimed directly at the earth, it is even recognizable from an extreme distance. "

Gamma-ray photons generated within the jets eventually collide with the cosmic nebula, leaving a visible impression.

This allowed astronomers to determine the density of the nebula not only at a particular location, but also in a particular place to measure time in the history of the universe.

"Gamma rays are the most energetic form of light." They are actually so energetic that their interaction with starlight has unusual consequences. When the right frequencies of light collide, they can be converted into matter by Albert Einstein's famous equation E = mc 2 "said Dr. Alberto Dominguez, astrophysicist at the Complutense University of Madrid.

Beam photons moving through a fog of starlight move are likely to be absorbed, "added Ajello.

"By measuring how many photons were absorbed, we were able to measure how thick the fog was and also measure how much light was present over the entire wavelength range. "

According to the new measurement, the number of photons – particles of visible light – that reach space after being irradiated by stars is 4 *. 10 84 .

"By using blazars at different distances from us, we measured all starlight at different times," Dr. Vaidehi Paliya, postdoctoral fellow at Clemson University.

We Measured the Tota The starlight of every epoch-a billion years ago, two billion years ago, six billion years ago, and so on-until the formation of stars. "

" This enabled us to reconstruct the EBL and determine the star-history of the Universe in a more effective manner than previously achieved.

The study was published in the journal Science .

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published. S. Abdollahi et al. . (The Fermi-LAT collaboration). 2018. A gamma-ray determination of the history of star formation of the universe. Science 362 (6418): 1031-1034; doi: 10.1126 / science.aat8123


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