The question of how much light the first stars produced is fundamental to models of the Universe's development. But observations have so far failed to agree: is the answer a lot, or not very much at all? On page 1018 of this issue, Aharonian et al. report the detection of copious high-energy γ-ray emission from two 'blazars' — a class of active galaxy — around 2 billion light years from Earth. This observation indicates that such radiation can travel largely unimpeded through the cosmos, and implies that the infrared glow of the first stars in the Universe and their remnants is fainter than previous measurements had led us to believe. If true, that could influence our ideas of how and when the first structures in the Universe evolved.
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