Purple Asters?

In the spring when the boys and I did some yardwork for my grandfather, I salvaged this plant that Pop didn't want anymore. Based on the leaves, he and I seemed to think it was a butterfly bush. But, lo and behold, a few days ago it started to bloom - I guess it's not a butterfly bush!! Maybe a purple aster or a type of mum? Whatever it is, it's a beautiful bright spot in my otherwise dried flower beds. I love surprises.