What is this?

I took some chai tea and my book out onto my patio this morning -- what a gorgeous morning it is, too! -- and while I was looking around at all the things that need cleaning up after this very wet summer, I saw this. I believe it's a moth, but I certainly don't know the exact name. It's really beautiful, and I've never thought moths are beautiful!

Let me know if you know its name or how to find out, please.

UPDATE: Ahhhhh! It's known as a Luna Moth, relative of the silkworm moth:
http://en.wikipedia.org/wiki/Actias_luna
http://www.brookfieldzoo.org/pagegen/images/2000002/Luna.jpg