George Johnson brings to life Henrietta Swan Leavitt, who found the key to the vastness of the universe—in the form of a “yardstick” suitable for measuring it. Unknown in our day, Leavitt was no more recognized in her own: despite her enormous achievement, she was employed by the Harvard Observatory as a mere number-cruncher, at a wage not dissimilar from that of workers in the nearby textile mills. Miss Leavitt’s Stars uncovers her neglected history.