Fingerprints of the First Stars in the Sky-Average Radio Spectrum
I will present the measurement of an absorption feature in the sky-averaged radio spectrum centered at 78 MHz with the EDGES experiment. The measured feature is broadly consistent with the absorption of photons from the microwave background by neutral hydrogen gas in the intergalactic medium (IGM) due to significant star formation about 180 million years after the Big Bang. Despite this consistency, the amplitude, shape, and frequency of the feature are in tension with physical predictions for either the temperature of the IGM or the microwave background at those redshifts. In my talk I will describe the EDGES measurement, carried out from the desert of Western Australia, and some of the proposed physical implications, if the measurement is independently verified.