What term describes the successful demonstration that astronomers could measure distances reliably far outside the immediate stellar neighborhood using Cepheids?

Answer

The cosmic distance ladder.

Hubble's triumph was the successful demonstration of the cosmic distance ladder, where the Cepheid variable served as the essential rung allowing measurement beyond the Milky Way's confines.

What term describes the successful demonstration that astronomers could measure distances reliably far outside the immediate stellar neighborhood using Cepheids?
measurementHubblegalaxyDistanceCepheid