Cepheid Variables as Standard Candles

Discovered by: Henrietta Swan Leavitt in 1908.

What is it? A type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.

Why is it important? The strong correllation between a Cepheid variable's luminosity and pulsation period established Cepheids as important indicators of cosmic benchmarks for scaling galactic and extragalactic distances. aka. Standard candles. [Image - Leavitt, Henrietta S; Pickering, Edward C, Public Domain, https://commons.wikimedia.org/w/index.php?curid=34747012]