[tejtm]

Every star that is not our sun is in a different solar system. Could you have meant to say a star in a different galaxy could toast us?

I think, ball park, a SN 500 light years out is considered safe e.g. Betelgeuse. Our Milky Way galaxy is thought to be roughly 100,000 light years in diameter so we should be safe from all but those within about a hundredth of the radius of our galaxy from us.

space is big ...

[bmitc]

I don't think they were using the solar system, as in our solar system, as their frame of reference.