For the first time, astronomers have detected a signal from stars emerging in the early universe. Using a radio antenna not much larger than a refrigerator, the researchers discovered that ancient suns were active within 180 million years of the Big Bang. Models of the early universe predict such stars were massive, blue and short-lived. Because telescopes cannot see them, though, astronomers have been hunting for indirect evidence, such as a tell-tale change in the background electromagnetic radiation that permeates the universe, called the cosmic microwave background (CMB). In their paper, the “Experiment to Detect the Global EoR (Epoch of Reionization) Signature” team reported seeing a clear signal in the radio wave data, detecting a fall in CMB intensity when that process began. As stellar fusion continued, its resulting UV light began to rip apart the free-floating hydrogen atoms, stripping away their electrons in a process called ionization.
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