Astronomers believe that our Universe began to form the first stars when it was a few hundred million years old.…
Astronomers believe that our Universe began to form the first stars when it was a few hundred million years old. Since then, the Universe has become a star-making tour de force . There are now about two trillion galaxies and a trillion-trillion stars. Using new methods of starlight measurement, astronomers analyzed data from NASA’s Fermi Gamma-Ray Space Telescope to determine the history of star formation over most of the Universe’s lifetime.
One of the main goals of the Fermi mission was to assess the extragalactic background light (EBL), a cosmic fog composed of all the ultraviolet visible and infrared light stars About the Universe’s history.
“From data collected by the Fermi telescope, we were able to measure the entire amount of starlight ever emitted,” said Dr. Marco Ajello, an astrophysicist at Clemson University.
“Most of this light is emitted by stars living in galaxies. Og så, dette har gjort det muligt for os at bedre forstå stellar-evolutionens proces og få fascinerende indsigt i, hvordan universet producerede dets luminøse indhold. “
Dr. Ajello and co-authors analyzed nearly nine years of data relating to gamma ray signals from 739 blazars.
“Blazars are galaxies containing supermassive black holes that are able to release narrowly collimated jets or energetic particles that leap out of their galaxies and
“When one of these jets happens to be pointed directly at Earth, it is detectable even when originating from extremely far away.”
Gamma ray photons produced within the jets eventually collide with the cosmic fog, leaving an observable imprint.
This enabled the astronomers to measure the density of the fog not just at a given place but also at a given Time in the history of the Universe.
“Gamma rays are the highest-energy form of light. De er så energiske, faktisk, at deres interaksjoner med starlight har unusual consequences. When the right frequencies of light collide, they can convert into matter through Albert Einstein’s famous equation E = mc 2 “said Dr. Alberto Dominguez, an astrophysicist at Complutense University of Madrid.
“Gamma ray photons traveling through a fog of starlight have a high probability of being absorbed,” Dr. Ajello added.
“By measuring how many photons have been absorbed, we were able to measure how thick the fog was and also measure, as a function of time, how much light there was in the entire range of wavelengths.”  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 * 10 84 .
“By using blazars at different distances from us, we measured the total starlight at different time periods, “said Dr. Vaidehi Paliya, a postdoctoral researcher at Clemson University.
“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 . “
” This study was published in the journal Science
S. Abdollahi et al. . (The Fermi-LAT Collaboration). 2018. A gamma-ray determination of the Universe’s star formation history. Science 362 (6418): 1031-1034; doi: 10.1126 / science.aat8123