Ground-based image of the Andromeda Galaxy stretches from lower left to upper right. A white arrow points to the location of the Hubble observations. Above the galaxy are four boxes containing Hubble images of the variable star at different luminosities.

Hubble Observes Cepheid star in the Andromeda Galaxy

Astronomers use cyclical changes in the brightness of Cepheid stars to determine astronomical distances. The arrow points to a Cepheid star in the Andromeda galaxy observed by Hubble (inset boxes).

Credits: NASA, ESA, Hubble Heritage Team (STScI/AURA), R. Gendler