NASA scientists have observed the light from the very first stars of the universe

Cosmic history Fermi diagram showing blazars

NASA scientists have found the light of the very first stars in the Universe. These stars are as old as our time is old, i.e. about 13.7 billion years old, when Big Bang occurred.

This research has been published online in Science.

At that time, shortly after the Big Bang the Universe was a cold place to allow the atoms to join together to form the very first stars. Those very first stars are glowing since that time and giving their lights to the Universe. Now the scientists have isolated that glow — called the extragalactic background light, or EBL — and separately detected it from the light by the other stars.

“The EBL is the ensemble of photons generated by all the stars and also all the black holes in the universe,” said astrophysicist Marco Ajello of the SLAC National Accelerator Laboratory in California, who led the research. “The EBL also includes the light of the first massive stars that ever shone. We have a fairly good knowledge of the light emitted by ‘normal’ stars. Thus, by measuring the EBL we are able to constrain the light of the first stars.”

Ajello and his collaborators detected the EBL by analyzing measurements of distant black holes made by NASA’s Fermi Gamma-Ray Space Telescope. Fermi observed light from giant black holes known as blazars that release huge amount of light after engulfing the matter.

“We use [blazars] as cosmic lighthouses,” Ajello said. “We observe their dimming due to the EBL ‘fog’. This allows us to quantify how much EBL there is between us and the blazars. As blazars are distributed across the universe, we can measure the EBL at different epochs.”

With the help of all this setup, scientists were able to study the light of the stars that are just 0.6 billion years old or so. Those stars are very much different than the today’s stars as they are vey massive, burned hotter and brighter and have a short life span.

This study could help in further researches about how quickly the first stars formed and when they were formed after the birth of the universe.

“We really need to understand this period,” said Volker Bromm, an astronomer at the University of Texas at Austin who did not participate in the research, during a NASA press conference announcing the results. “At this point we have theoretical models, but we need to test them and constrain them.”

“With Fermi we have the first step into this cosmic frontier,” Bromm added.

“We’re very excited about the prospect of extending this measurement even farther,” said Julie McEnery, the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

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