I'm not an astronomer, and may or may not be smart. 1. I don't know; Google probably does know. 2. Those jets aren't in a complete vacuum. They're running

I'm not an astronomer, and may or may not be smart. 1. I don't know; Google probably does know. 2. Those jets aren't in a complete vacuum. They're running into galactic gas, of which, on a galactic scale, there is quite a bit. 3. Several reasons. One, they aren't a perfect "beam". They spread out. If you're a few billion years away, they spread out quite a bit in that distance. Then, to get to us, they go through their galaxy's gas, intergalactic space (not totally empty), our galaxy's gas, and finally our atmosphere. Each of those reduces the amount of radiation. Oh, yeah, our magnetosphere deflects charged particles, too.