This is definitely a book by [David Zindell](https://en.wikipedia.org/wiki/David_Zindell), most likely *Neverness.*  The woman who becomes a godlike cybernetic entity is called the "Solid State Entity" (encompassing not just a planet, but an entire solar system) and she's one of several such AI deities in the book, and in that larger fictional continuity, which is also the setting for his trilogy, *A Requiem For Homo Sapiens* (*The Broken God*, *The Wild*, *War in Heaven*).

One of the most distinctive aspects of the continuity is the existence of a guild of hyperspace pilots who navigate through the universe by discovering new and unique mathematical theorems.

*Neverness* is one of my favorite books, but I never read the trilogy, so the only reason I hesitate at all about the identification is because I don't remember the supernova viewing party.  The mathematical pilots and the Solid State Entity are both in *Neverness*, but they are likely to also appear in the trilogy as well.