Whose observations first proved galaxies exist beyond ours?

For a long time, astronomers debated whether the fuzzy patches of light called nebulae were within our own Milky Way or were separate galaxies far beyond it. In the 1920s, the American astronomer Edwin Hubble settled the question using the powerful telescope at the Mount Wilson Observatory. By identifying special pulsating stars called Cepheid variables in the Andromeda nebula, he could measure its distance and showed it was far too distant to be part of the Milky Way, proving it was a separate galaxy. This revealed that the universe is vastly larger than previously imagined, filled with countless galaxies. Hubble went on to make another monumental discovery: that distant galaxies are moving away from us, and the farther they are, the faster they recede, providing the first strong evidence that the universe is expanding. The Hubble Space Telescope is named after him.