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Finally an Answer to why Gamma Rays are Coming From Seemingly Empty Space

18 Sep 2021, 15:05 UTC
Finally an Answer to why Gamma Rays are Coming From Seemingly Empty Space
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Gamma rays strike Earth from all directions of the sky. Our planet is bathed in a diffuse glow of high-energy photons. It doesn’t affect us much, and we don’t really notice it, because our atmosphere is very good at absorbing gamma rays. It’s so good that we didn’t notice cosmic gamma rays until the 1960s when gamma-ray detectors were launched into space to look for signs of atomic weapons tests. Even then, what we noticed were intense flashes of gamma rays known as gamma ray bursts.

Gamma-ray bursts are bright but short-lived. They are so bright that it was first feared they were caused by nuclear blasts on Earth, but we now know they are caused by large dying stars as their core collapses into a black hole. The collapse can trigger the formation of jets of material streaming away from the star at nearly the speed of light. When the jet collides with interstellar gas, it creates a beam of gamma rays. If the jet of a dying star happens to be pointed in our direction, we detect a gamma-ray burst.

As our gamma-ray telescopes became more sensitive, we also detected a galactic gamma-ray glow. Most of these gamma ...

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