Henrietta Swan Leavitt – Measuring Stars 

“She had the happy faculty of appreciating all that was worthy and lovable in others, and was possessed of a nature so full of sunshine that, to her, all of life became beautiful and full of meaning.” – Solon I. Bailey in the obituary of Henrietta Leavitt

Henrietta Leavitt (04 July 1868 – 12 December 1921, a dedicated researcher at Harvard College Observatory, made groundbreaking contributions to astronomy. Henrietta Leavitt was tasked with cataloging, observing, and tabulating stars that varied in brightness over time, known as Cepheid variables. Photographic plates taken over an extended period at the Arequipa Observatory in Peru captured night sky images, which were then sent to Boston. Leavitt identified many new Cepheid variables, increasing the number of known Cepheid variables in the Large and Small Magellanic Clouds to nearly 1,800. She discovered that these stars oscillated over periods ranging from days to weeks and that the duration of these oscillations was related to their brightness (or luminosity): the longer the period from minimum to maximum brightness, the brighter the star. She found this pattern, since all stars she observed were at approximately the same distance from Earth. She published her findings in 1908 and in 1912.

The comparison of the apparent brightness of a Cepheid star to its absolute brightness – based on its pulsation period – could now be used to measure the distance of these stars. Up to this time, the only possibility to measure distances was using the star’s parallax, a method that only allowed to measure distances up to a few thousand light-years. With using Leavitt’s relationship between luminosity and pulsation period in Cepheid stars, distances up to 13 million light-years could be measured: she thus revolutionized astronomy.

In 1924, Edwin Hubble discovered a Cepheid variable in the Andromeda galaxy and, with the help of Leavitt’s finding, showed that this object lies far beyond our Milky Way.

Her father was a Congregationalist minister. While we know she was a deeply committed Christian throughout her life, details about her faith are scarce. She was passionately devoted to her work, carrying it out with meticulous precision. Despite significant health challenges, including hearing loss and a prolonged battle with cancer, she persevered. Her legacy is a testament to her kindness, intellectual curiosity, and the power of scientific inquiry.

Had she lived longer, she might have been awarded the Nobel Prize. The mathematician Gösta Mittag-Leffler, a member of the Swedish Academy of Sciences, planned to nominate her for the Nobel Prize in 1924, but her untimely death three years earlier prevented this. The Nobel Prize is not awarded posthumously.

Henreitta Leavitt has a moon crater and an asteroid named after her.

| Written by B M Moritz | Science meets Faith | Read full story at Read More