The Cepheid Variables and Henrietta Swan Leavitt

I thought this was a very interesting article on the history of the Cepheid variables and discovery of the period-luminosity law and hence the evidence that there were other galaxies out there beyond the Milky Way, and that the universe was expanding.

https://www.bbc.com/future/article/20210310-the-star-fiend-who-unlocked-the-universe

Leavitt was one of many "human computers" working at the Harvard College Observatory in the late 19th and early 20th centuries. This group, all women, discovered dozens of new novae, nebulae, and asteroids, as well as thousands of "variable stars", which are defined by their waxing and waning brightness. Leavitt, who was once described as a "variable star-fiend", discovered over 2,000 variable stars of her own. And her hunt for stars led her to an even greater prize – the method for measuring distance through space.

Known as the period-luminosity relationship, Leavitt’s insights allowed astronomers to measure distance on an intergalactic scale and gave Hubble the formula he needed to see outside our neighbourhood and into the Universe beyond. “Our entire perception of the Universe completely changed as a result of her discovery,” says Wendy Freedman, an astronomer and astrophysicist at the University of Chicago.

AMKC

So cool. I honestly thought this would be way above me and I would understand none of it but its seems not too bad.
Great find.

DubOnHoliday

Highly recommend this book which tells of the incredible contribution of women in those years... https://www.amazon.co.uk/Glass-Universe-Dava-Sobel/dp/0007548206/ref=asc_df_0007548206/?tag=googshopuk-21&linkCode=df0&hvadid=310831438545&hvpos=&hvnetw=g&hvrand=5738126468016913375&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=20496&hvtargid=pla-483553637204&psc=1