Seems well within range; and yes they travel at C - there have been some LIGO observations that were successfully correlated with more traditional (e.g. optical or radio) observations.
So it's even worse: the Galactic Empire has built an even bigger Death Star which can destroy an entire star (or cause it to collapse into a black hole)?
With that in mind, I can imagine that millions of voices suddenly cried out in terror and were suddenly silenced.