Y'know, for those of you asking how far it is from Earth/Sol to Sirius, I did the calculations based on available data a long while back, when I was still an active member of the OSD here...
Since we can only go off of a mix of ingame/story references and try to compare them to nasa's (limited) information on our galaxy, that's the closest estimate you'll find.
I doubt you'd be seeing a supernova from Sol anytime soon. However, The Order already knew about Sol's destruction (as do the SCRA/coalition), it's just been a tightly guarded secret from the civilian populace.