Henrietta Leavitt's work on celestial mapping

Henrietta Leavitt studied stars called Cepheid variables, which pulse regularly with changing brightness. She discovered a direct relationship between a Cepheid’s pulsation period and its intrinsic brightness: longer-period Cepheids are brighter. By measuring their apparent brightness, astronomers can determine their distance from Earth, using Leavitt's discovery as a cosmic yardstick. This work was crucial in measuring distances to faraway galaxies, helping to map the universe’s structure. Leavitt’s insight provided a key step in understanding the scale of the cosmos and laid the groundwork for modern extragalactic astronomy.