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When Did The First Stars Appear In The Universe?

28 Dec 2017, 00:30 UTC
When Did The First Stars Appear In The Universe?
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An artist’s impression of the environment in the early Universe after the first few trillion stars have formed, lived and died. The existence and life cycle of stars is the primary process that enriches the Universe beyond merely hydrogen and helium, while the radiation emitted by the first stars makes it transparent to visible light. Image credit: NASA/ESA/ESO/Wolfram Freudling et al. (STECF).Today, our visible Universe contains 2 trillion galaxies, each with billions of stars. But when did the very first one appear?When we look out at our Universe today, there are an estimated two trillion galaxies within it, with each one containing an average of hundreds of billions of stars. All told, that means we can see some ~1024 stars within the visible Universe, going all the way back as far as our greatest observatories, even in principle, could ever take us. As we look to greater and greater distances, we’re also looking back in time, and since the Big Bang occurred a finite amount of time ago (13.8 billion years), there’s a limit to how far back we can look and still see stars. There must have been a time before which there were no stars, and therefore, a ...

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