I was originally leaning towards labeling it a super-jovian, but the more I think about it, the more I realize it wasn't a star or planet at all, but some kind of space entity that the locals mistook for a planet. Hmmm ... Forgive me for going wibbly-wobbly on everyone here, but might we have just witnessed the birth of the Great Intelligence? The Doctor poured all his memories into it, but it wanted more. So Clara gave it all the things that could have been, but weren't, and then it ... what? Vanished? Died? Went somewhere else? Somewhen else?