At the center of these side-by-side images is a special class of star used as a milepost marker for measuring the universe’s rate of expansion – a Cepheid variable star. The two images are ...

Leavitt discovered 2,400 variable stars, about half of the known total in her day. Through these discoveries came her most important contribution to the field: the study of cepheid variable stars ...

Leavitt's work with variable stars led to her most important contribution to the field: the cepheid variable period-luminosity relationship. By intense observation of a certain class of variable ...