The people came thinking that different nebulas are other galaxies?

Question

That our Sun and stars and that the explosions of rays gamma are black holes being born, but the scientists start again to think about other possibilities; everything can be certain does not go to pass of great astronomical mirages that everything in the Great Atom summarizes “Universe”, finite in its dimension and the infinite in its time. Everything in the Mechanics of the Diagram of this Great Atom, and nothing beyond the same (I Tarcísio Brito). E you! It agrees or it disagrees?

Answer 1

The question of whether some nebulae were actually "external galaxies" was one of the big controversies in astronomy in the first few decades of the 20th century.

This question was definitively settled with the commissioning of large telescopes like the Mt. Wilson 100 inch, that were capable of resolving and measuring individual stars in some of the nearer galaxies. Of course some nebulae are not galaxies, but glowing gas clouds in our own Milky Way galaxy.