From context, I 'm pretty sure its light-years, not miles, and this was a typo. The curvature of the pulses in the frequency domain implies that there's lots o

From context, I 'm pretty sure its light-years, not miles, and this was a typo. The curvature of the pulses in the frequency domain implies that there's lots of ionized gas between the us and the source. Lower frequencies are delayed relative to higher frequencies. Also, "mysteriously noisy galaxy 3 billion miles away" (emphasis mine).