To further this point, there was an incident in early human history where it was debated whether the massive blobs in space where gas giants or galaxy. It went so far, in fact, that a mass of people built a telescope to clearly see the blobs just to prove eachother wrong and find out that both ideas were correct.
I'm aware of the irony of correcting you but I can't help it. Nebulae not gas giants. Gas giants were known to be planets at the time, as they have apparent motion relative to the Stars. Nebulae and galaxies don't have apparent motion relitive to the stars.