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Why Scientists Tried to Measure All of the Starlight That Ever Shone

Fermi-LAT view of gamma-ray sky. Image: Fermi-LAT Astronomers this week announced that they would attempt to measure all of the…

Fermi-LAT view of gamma-ray sky. Image: Fermi-LAT

Astronomers this week announced that they would attempt to measure all of the starlight in the universe.

You might wonder why. Ultimately, they’re trying to tell the universe’s story.

“We wanted to know how star formation history continued,” Kari Helgason, scientist at the Max Planck Institute for Astrophysics in Germany, told Gizmodo.

The whole universe is diffuse with “extragalactic background light” or EBL, photons emitted by all of the galaxies’ stars in infrared, optical, and ultraviolet wave lengths. Going back in time, this light is the sum of all of the light emitted by stars from the Big Bang up to the moment and distance you look-remember, distance is the same as time in space, so looking at a farther region of space means looking at fewer stars. The EBL can weaken gamma rays. So, scientists measured the gamma rays coming from distant quasars to see if they carried the signature of a shadow from this starlight. Met deze informatie kunnen de wetenschappers een verklaring geven over de snelheid van star formation over time .

Researchers analyzed gamma rays from nine years of data collected by the Fermi Gamma-ray Space Telescope. Specifically, they looked at 739 blazars, which are black holes spewing jets or matter pointed at the Earth, and one gamma-ray burst. These objects dated back 200 million to 1

1.6 billion years. De anvendte en ligning til alle de data, der beregnet den samlede baggrundslys, ifølge den nye undersøgelse, der blev offentliggjort i Science.

The results were consistent with past attempts to measure the extragalactic background light, showing that star formation hit its maximum around 10 billion years ago.

Elisa Prandini, astroparticle physicist from the University of Padova, Italy, in a commentary for science. De metingen biedt een limiet aan hoe veel flauwe galaxies er waren rond 12 miljard jaar geleden. These galaxies are thought to have caused a “reionization era,” an important time in the history of the universe when, after the first atoms formed from protons combining with electrons, energy from the new galaxies split them back up.

On top of that, the extragalactic background light could provide a new way to hunt never- before-seen particles, said Prandini.

The study has its caveats, said Helgason-they assumed all of the background light came from starlight, but powerful black holes, too, can spew radiation into space. Aktuelle estimater tyder på at de ikke er en stor bidragsyter, men de er verdt et dypere utseende bare i tilfelle.

So, no, you’re not just going to add up all the universe’s starlight for nothing.

[Science]

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