One of the most important pioneers of cosmology is often overlooked these days. Henrietta Swan Leavitt worked as a “computer” in the Harvard College Observatory. She started by examining photographs of stars in order to measure the relative brightness of stars (luminosity). She looked at a cluster of stars known as the Magellanic Clouds.
These stars are known as Cepheid Variable Stars, which is a fancy term for pulsing stars. These stars have changing observable luminosities. Leavitt noticed a relationship between there peak luminosity and the oscillation period. It seemed that stars with greater peak luminosity had a longer period. She relied on the assumption that they were all fairly close together and deduced that the period of the star could tell you something about the stars TRUE luminosity, not just the observed one.
Today this is known as the Period-Luminosity relationship or Leavitt’s law. It says that the logarithm of the period of a Cepheid variable star is directly related to its intrinsic luminosity. This became one of the few standard candles in astronomy, which was extremely important in allow researchers to deduce the brightness of stars that were really far away. Up until this point it was hard to tell if a star was dull because it was actually dull, or just because it was really far away.
Since her time scientists like Hertzsprung and Edwin Hubble have used Cepheid stars to establish portions of their own work. It led to the end of the one galaxy debate as we discovered the Andromeda Galaxy, and ultimately held Hubble reach the Big Bang Theory. In 1921, after falling increasingly ill, Henrietta Leavitt passed away. Due to the lack the of acknowledgment for her work and his lack of knowledge of her death, Swedish mathematician Gösta Mittag-Leffler tried to nominate her for the Nobel Prize. She never received a nomination because the prize committee does not award the prize post death (one exception).
About this contributor: I have just finished my final year of high school. I love playing ultimate frisbee, skiing and playing the clarinet/guitar. I am happiest when learning random trivia or stargazing. Learning for me is its own reward, whether it is about the quantumly tiny or the cosmologically large.