Discoveries and achievements

Calculating Halley’s Comet return (1759)

Nicole-Reine Lepaute worked with astronomers Clairaut and Jérôme Lalande to precisely calculate the date of Halley’s Comet return.

She spent entire months doing manual calculations, correcting mistakes and refining trajectories. Thanks to this work, the comet was observed almost exactly on the predicted date — a scientific feat for the time.

Writing the Treatise on Horology (1755–1757)

She collaborated with her husband Jean-André Lepaute, the King’s clockmaker, on a treatise about measuring time and how astronomical clocks work.

Her mathematical knowledge helped improve the accuracy of pendulums used for celestial observations, at a time when timekeeping was at the heart of scientific progress.

Astronomical ephemerides calculations (1760–1774)

Nicole-Reine Lepaute contributed to the production of official astronomical tables. Ephemerides indicate the daily position of planets and stars, useful for navigators, astronomers, and engineers.

She devoted many years to this meticulous work, often in the shadows. This mechanism of erasure illustrates the Matilda Effect.

Studies on eclipses and celestial phenomena

She revised predictions of solar and lunar eclipses by improving calculation methods. Her work demonstrates scientific rigor and strong mastery of celestial mechanics.

“She calculated the stars, but History forgot her name.”

— Closing line (Matilda mockup)

Collaboration with Jérôme Lalande

Throughout her career, Nicole-Reine collaborated with Jérôme Lalande, one of the great French astronomers. She assisted him in writing his books and in his research on planetary orbits.

Her role, often discreet, was essential to the success of this work — a reality this project aims to make visible.