Light from first stars detected in cosmic
New research from NASA's Fermi Gamma-ray Space Telescope has now gotten closer than ever before to describing when that first star flickered on, a new study says.
Based on data gleaned from jets of high-energy radiation emitted long ago, scientists say they now know that stars were present at least as early as 500 million years after the big bang, which gave birth to the universe some 13.75 billion years ago.
The findings also put an upper and lower limit on the amount of light present at that 500-million-year mark, and consequently the size and number of early stars. The stellar population, the researchers confirmed, was quite small, Kazinform quotes the National Geographic.
"We haven't been able to establish yet when the first stars began to shine, but we have peeked into the epoch of our universe when it happened," said study co-author Marco Aiello, an astrophysicist at Stanford University.
The Fermi findings, then, get us a step closer to pinning down the powering up of the first stars. That future discovery should shed new light on the dark period that preceded first light-and on the big bang that preceded everything.
Foggy Reasoning
The telltale new data comes from the first ever direct measurement of long-theorized "extragalactic background light," according to the study, published Thursday by the journal Science.
Carrying information about its origins, "the optical and ultraviolet light from stars continues to travel throughout the universe even after the stars cease to shine, and this creates a fossil radiation field," Allejo said.
To measure this light, the Fermi team studied blazars-ancient galaxies that appear superbright because the high-energy jets shooting from their central black holes are aimed directly at Earth.
Gamma rays-high-frequency electromagnetic radiation-from blazar jets shine like lighthouse beacons through the "fog" of the cosmic background light, the researchers say.
Speeding through space, the gamma rays collide with that remnant starlight and lose some of their energy-rays that have lost most of their gamma radiation, then, must be from the oldest blazars.
It's these old rays that the Fermi satellite has used to determine the "thickness" of the cosmic light fog, all the way back to 500 million years after the big bang-a stand-in for measuring the stars themselves, which is currently impossible.
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