Sky & Telescope - December 2021 - 12

PORTRAIT: HARVARD UNIVERSITY ARCHIVES; ILLUSTRATION: DAVID CURTIS
ASTRONOMICAL PIONEER by Dava Sobel
Henrietta Swan Leavitt
Remembering
How one talented astronomer's meticulous work left an important legacy.
I
n the century since Henrietta Leavitt died, the observation
that she first published in 1908, then elaborated in
1912, has achieved the status of an astrophysical law. Her
quiet life has become the subject of books, stage plays, art
exhibitions, poems, a doll, and at least one song. It was Leavitt
who discovered a yardstick for gauging distances across space,
enabling the first realistic appreciation of the size of the Milky
Way, and, soon afterward, the breadth of the chasm separating
our home galaxy from other island universes.
I first encountered Henrietta Leavitt at a meeting with
astronomer Wendy Freedman, who
is now the John and Marion Sullivan
Professor of Astronomy and Astrophysics
at the University of Chicago.
At the time of our interview in the
early 1990s, Freedman headed the
Hubble Space Telescope Key Project
to Measure the Hubble Constant to
determine the expansion rate of the
universe. She mentioned Leavitt as the
person who had first documented the
noteworthy trait of Cepheid variables
that makes such stars useful as deepspace
distance markers. Freedman
stressed the point for my benefit: The
entire research protocol for the Key
Project rested on observations made by
a little-known woman at the turn of
the 20th century.
Meeting Miss Leavitt
Her full name, Henrietta Swan
Leavitt, suggests she added a husband's
12 DECEMBER 2021 * SKY & TELESCOPE
surname to her own maiden name, but in fact she never
married. She remained " Miss Leavitt " to her associates
at the Harvard College Observatory in Cambridge, Massachusetts,
throughout the 20-odd years of employment
there. Everyone liked her. It was said she had a nature full of
sunshine and a talent for seeing the worthiest, most lovable
features in others. Her ability to descry the changing brightness
of variable stars bordered on the miraculous. However,
as her biographer, George Johnson, noted in the preface to
his 1995 book Miss Leavitt's Stars, his chosen subject had
left no diaries and only a few letters to
help tell her life story.
Leavitt was born on the 4th of July in
1868, in Lancaster, Massachusetts, the
first of seven children and the namesake of
her mother, née Henrietta Swan Kendrick.
Her father, the Reverend George Roswell
Leavitt, moved the family to Cambridge
and later to Cleveland, Ohio, serving in
both those cities as pastor of Congregational
churches. In 1885, 16-year-old
Henrietta enrolled at the Oberlin Conservatory
of Music in Ohio. She had grown up
singing hymns but soon developed trouble
hearing them, and over time she became
increasingly deaf.
She switched to Oberlin College, where
LEGAL SCHOLAR From her desk at the
Harvard College Observatory, Henrietta
Swan Leavitt discovered that Cepheid
variables can serve as deep space distance
markers. Her celebrated period-luminosity
relation is now becoming widely known as
the Leavitt Law.
she excelled at mathematics, and after two
years returned to Cambridge to continue
her studies at the Society for the Collegiate
Instruction of Women (later Radcliffe College).
She lived with the family of her uncle
Erasmus Darwin Leavitt, Jr., a respected
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