what size of wire is used when making the shooting stars i see on cakes and where did you buy them? do cover them with anything before inserting into cakes?

I don't think there's a set size; it's whatever size stands up or arches the amount you want. Cakers often use floral wire, but the wires are not stuck directly into a cake. Please see
http://cakecentral.com/cake-decorating-ftopict-632290.html
I know it's a long thread, but there's some useful information in there.