Alright, I will try to answer all of your questions, one at a time, as best as I can.
1. Was their any particular reason that the Fenyar sun went super nova suddenly? I think that I read something about a missile making the sun explode or something, but I'd like to find out the specifics.
Answer: Yes, you are right on. The Fenyaro, mostly Dy'Unnar, stole a space probe from a human lab, loaded a nuclear device onto it, and fired it at the sun in hopes of cutting off the sun and lowering the temperature to kill off the humans, while they relied on their coats of fur to survive the ensuing winter. The warhead went off poorly, and set in motion the process by which the sun went supernova. Before the sun could explode however, a balance was reached, and things teetered on the edge. Then, due to the stress caused by the Star Army presence so near, the explosion occured.
2. It's just that NovaCorp now mainly resides in the graveyard of that system, and their have been some rumours spread about it being haunted and dangerous, and I'd like to know what to expect.
Answer: I don't know where the rumors started, off the top of my head, but I think they were there to discourage people from "snooping" around too much in the graveyard of my planet while I wasn't here to oversee it. One thing is, it can't be haunted, because ghosts really aren't all that scientific, so if anything, there would be only small, short, spirit manifestations of the most well known figure of Fenyar, ie, Sergei Dimitriov, last king and ruler of the planet. It would be dangerous, only in the sense that there could still be black holes and solar radiation, but with the technological advances in sheilding and armor plating, I don't see these as much of a risk anymore.
3. Also the Fenyarians (or something like that), used to have some form of invulnerable metal called Teraneum or something. What happened to this?
Answer: Yes, the Fenyar races did have access to Terrainium, but it was far from invulnerable. While it was/is very resistant to energy and projectile weaponry, it is a very good conductor of electricity, and therefore that would be a weakness. It also didn't protect against antimatter. As for what happened to it, the supernova destroyed most of it on the planet, and then the small traces of what was left were sucked into a black hole. There are rumors (ICly) that there might still be some Terrainium in a Kee'Awloo vault on an uncharted planet.
4. Are the blueprints of how to make it still out their somewhere?
Answer: Yes, there are two copies of the blueprints for recreating Terrainium. One of them is in the possession of a "mad" scientist named Shadow Ex, and would be fairly easy to get ahold of if you could get in contact with him, and made him an appealing offer. The other copy of the blueprints, and one that would be much harder to get ahold of, is in the Kee'Awloo vaults on a planet that has yet to be found and explored by the Star Army. Both ways are feasable with time, effort, and a little funding.
5. Is it possible that some survived the SuperNova?
Answer: It is possible that a small amount of Terrainium could have survived the supernova, but due to the black hole, and the rumors of the space being haunted, it would be too late to find them before they would be sucked into the void.