It's a pretty near literal name
Consider the last moments of Alderaan.
From the command-bridge of the Death Star, Alderaan looked like this:
Assuming that's a window, not a viewscreen with zoom-control, Alderaan looks mighty far away.
Not so different to how our moon looks to us on earth.
So assume the Death Star, which is around 1:20th the size of our moon was orbiting at the same distance as said moon..
We could definitely see it at night.
It'd be a bright white dot. Metal is pretty reflective.
You probably wouldn't see any details, maybe the darker circle of the dish, or a band across the middle for the trench.
You'd probably need a telescope to make out those details.
But for the average person looking up one day and noticing the strange bright white dot in the sky?
It's a star.
You're looking at the bright white star, and then it turns green, and you die.
It's a star that kills.
An accurate description of what you'd experience if you were on the receiving end.