How did Edwin Hubble prove Andromeda was a galaxy?

How did a Cepheid variable star help Edwin Hubble prove the Andromeda Nebula was a galaxy?  Roger BradySan Quentin, California Cepheids are rare variable stars with periods ranging from about 1 to 120 days. Their light curve — a chart showing brightness over time — is characterized by rapid brightening followed by slow dimming inContinue reading “How did Edwin Hubble prove Andromeda was a galaxy?”
The post How did Edwin Hubble prove Andromeda was a galaxy? appeared first on Astronomy Magazine.