Katherine Johnson, the pioneering mathematician whose career at NASA was the subject of the 2016 book Hidden Figures, died on Monday at the age of 101, the New York Times reports.

Johnson was one of the first African American women employed by NASA, which she joined in 1953 when it was called the National Advisory Committee for Aeronautics. She worked as a “human computer,” performing complex calculations by hand. Her work was central to several of the agency’s most famous projects, including John Glenn’s flight around Earth, as well as the Apollo 11 and Apollo 13 missions.

Long known to observers of the American space program, Johnson became a national celebrity of sorts with the 2016 publication of Hidden Figures, Margot Lee Shetterly’s bestselling book about Johnson and her fellow mathematicians Dorothy Vaughan and Mary Jackson. The book formed the basis for a hit film, also released in 2016, that starred Taraji P. Henson as Johnson.

Johnson was herself an author. In 2019, she published Reaching for the Moon: The Autobiography of NASA Mathematician Katherine Johnson, a book for young readers which a reviewer for Kirkus called a “national treasure.”

On Twitter, admirers of Johnson posted tributes to the legendary mathematician. U.S. Sen. Kamala Harris tweeted, “A barrier breaker and inspiration for women of color everywhere, Katherine’s legendary work with NASA will forever leave a mark on our history. My heart goes out to her family and loved ones.”

And Hidden Figures author Shetterly wrote, “My life’s honor to tell the story of Katherine Johnson's contributions to NASA, science, our country, and #HamptonRoads VA. Her brilliance helped us to see and celebrate other #hiddenfigures in history. You changed the narrative... Godspeed, Katherine Johnson.”

Michael Schaub is an Austin, Texas–based journalist and regular contributor to NPR.