Call that a moon?

So, looks like the first alien moon to be discovered is a gas giant orbiting a really, really big gas giant.

Or maybe that’s not so surprising, since I guess we still have an easier time finding gas giants of all kinds rather than smaller planets and moons. 

Anyway:

Astronomers have pinpointed what appears to be the first moon detected outside our solar system, a large gaseous world the size of Neptune that is unlike any other known moon and orbits a gas planet much more massive than Jupiter.

Given this, doesn’t it sort of seem like one might call this a two-planet binary sort of thing, rather than a planet with a moon? Do we already have a term for binary planets? Seems like that would apply here.

Pretty neat no matter what you call it.

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