Henrietta Leavitt was born in
Cambridge, Massachusetts, the daughter of a Congregational minister.
She attended Oberlin College and the Society for Collegiate
Instruction of Women (later Radcliffe College). As a senior in 1892,
Leavitt discovered astronomy. After graduation she took another
course in it, but then spent several years at home when she suffered
a serious illness that left her severely deaf. She hadn't forgotten
about astronomy, though. She volunteered at the Harvard College
Observatory in 1895. Seven years later she was appointed to the
permanent staff (at a salary of 30 cents an hour) by director Charles
Pickering. She got little chance to do theoretical work, but did
become head of the photographic photometry department. This group
studied photo images of stars to determine their magnitude.
During her career, Leavitt
discovered more than 2,400 variable stars, about half of the known
total in her day. These stars change from bright to dim and back
fairly regularly. 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 star, the cepheids, Leavitt discovered a direct
correlation between the time it took a star to go from bright to dim
to how bright it actually was. Knowing this relationship helped other
astronomers, such as Edwin Hubble, to make their own groundbreaking discoveries.
Leavitt also developed a standard
of photographic measurements that was accepted by the International
Committee on Photographic Magnitudes in 1913, and called the Harvard
Standard. To do this she used 299 plates from 13 telescopes and used
logarithmic equations to order stars over 17 magnitudes of
brightness. She continued refining and enlarging upon this work
throughout her life.
Leavitt was not allowed to pursue
her own topics of study, but researched what the head of the
observatory assigned. Because of the prejudices of the day, she
didn't have the opportunity to use her intellect to the fullest, but
a colleague remembered her as "possessing the best mind at the
Observatory," and a modern astronomer calls her "the most
brilliant woman at Harvard." She worked at the Harvard College
Observatory until her death from cancer in 1921.