107: Biggest Bang Ever! (Again?)

Astronomers have spotted what seems to be a supermassive black hole devouring a huge gas cloud — and in the media it's being claimed as the Biggest Explosion in the History of Explosions. Except, is it though? And didn't we already talk about this, way back in Episode 61? And anyway, what does "biggest" even mean? Or "explosion", for that matter? Or "time"? It's all very confusing. Emily's here to make sense of it all.