Early stars stole gamma rays from blazars

We have a lot of reasons to be interested in the earliest stars that formed in our Universe. Particularly, these stars were the first to fuse hydrogen and helium into (nearly) all the heavier elements that exist today, including the carbon, oxygen, iron, calcium, and the like that make up life as we know it. However, not only are these stars too far away to observe directly, much their light is hidden by foreground sources, including our Milky Way. A new indirect observation may have solved that problem, though:

Now a study using the Fermi Gamma-ray Space Telescope has used the light emanating from supermassive black holes known as blazars to measure the diffuse light produced by reionization. When high energy gamma rays interacted with the ultraviolet photons produced by early stars, they were converted to particle/antiparticle pairs, and this creates a dropoff at a specific point in the blazar spectrum. This absorption was evident in a sample of 150 blazars, and the data can help constrain models of the very first stars in the Universe. [Read more…]

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