I think we all know that FS2 Capella is not the real world Capella.
And we all seen how fast and how deadly the Supernova blast is. Realistic or not it is canon.
Seems like someone is pissed at people using the game is canon argument against him.
Unfortunately you're wrong.
1. Capella expands the instant the Saths finish doing the glowy thing trick. The saths are quote clearly at least a couple of light minutes away from Capella judging from the size of the star. No matter what the Saths did to Capella it would take several minutes for that to have reached the Saths. Which means that either
a) The artists making the cutscene didn't bother with the speed of light and just made a cool animation.
b) The glowy thing was not the cause of Capella's expansion. It was done AFTER Capella had already gotten bigger and happened to complete at exactly the same time that the light from Capella reached the Saths. Possible but somewhat unlikely.
2. While the explosion appears to expand very rapidly watch the amount of time it takes for the leading edge to travel from one side of the ringed gas giant to the other side. It actually takes several seconds. That explosion can not be moving at high FTL speeds if it takes several seconds to cover that kind of distance.
3. More to the point how the **** do you see an FTL explosion anyway? By the time the light reaches you the explosion has already passed you. So those planets should have started to boil while Capella hadn't even appeared to explode yet instead of when the blast wave hits them.
Again that means that you can either
a) Say that the artists making the cutscene didn't bother with the speed of light and just made a cool animation.
b) Say that the explosion is somehow FTL in how quickly it expands but STL in how quickly it damages anything.
4. The supernova destroys the ringed gas giant and then hits the GTVA forces. You can make a rough estimate how far out those gas giants are based on the size of capella. If you're taking the cutscene as an indication of how fast the supernova travels then that means that the Supernova can travel a distance of several thousand million km in seconds. That puts it well above light speed. However from the final mission we know that the supernova also takes about minute to reach the player.
That puts the Vega node pretty damn far out. So far out that for Capella to not be a tiny little dot in the mission it has to have somehow expanded to several hundred times it's real size. While that might explain why ships 6km in size are also visible in the mission against a star millions of kilometres in diameter I don't think anyone is going to take that idea very seriously.
So basically the upshot of this massive preamble is that you can not determine the speed of the supernova from the cutscene because it is neither internally consistant and it contradicts the mission. Sometimes it's faster than light, sometimes slower. Most likely this is simply for the same reason there is a crashed Hades in the intro. The animators just made a cool cutscene and didn't give a damn about the storyline as long is it fit somewhat into what they were doing.