Blog Post 13, Biography of Ejnar Hertzsprung

For this blog post, we had to write a post about a famous astronomer in the form of a short form biography. While I strongly considered investigating the lives of Johannes Kepler or Isaac Newton, having just talked about the astounding impact their thoughts had on society in my fantastic History of Science class, I decided to go for someone whose name I have heard quite a bit, but knew next to nothing about: Ejnar Hertzsprung. Hertzsprung's name is commonly heard connected to the Hertzsprung-Russell Diagram, graphing the relationship between the absolute magnitude or luminosity of a star vs. the star's surface temperature. One example is shown below:

Source: http://www.wwu.edu/skywise/a101_hrdiagram.html

The Hertzsprung-Russell shows that instead of being random, a distinct relationship exists between the temperature and the luminosity of a star, allowing us to group stars into several different groups by their observed characteristics. The majority of stars, including the Sun, appear on the Main Sequence, where stars spend much of their lifetime, but several other groups appear in unique locations on the diagram including giants, supergiants, and white dwarves. A star's location on the Hertzsprung-Russell diagram can be used to infer many properties of the star itself, using only two observed characteristics, temperature and luminosity.

Source: http://www.phys-astro.sonoma.edu/brucemedalists/Hertzsprung/hertzsprung.jpg

Ejnar Hertzsprung was a Danish astronomer and chemist who lived from 1873-1967. Though his name is heard often throughout the astronomy sphere, he worked primarily as a chemist for the first part of his life. He studied chemical engineering at Copenhagen Polytechnic, later continuing his work in chemistry in both St. Petersburg and Leipzig, focusing on the chemistry of photography. In 1901, he returned to Denmark to pursue an independent career in astronomy. For the next few years, Hertzsprung applied his knowledge of photography to investigate the relationship between a star's color and brightness. The relationship that Hertzsprung discovered (shown in the diagram at top) is now used as a basis for spectroscopic parallax, a method for estimating the distance of a star from the Earth.

In 1909, Karl Schwarzschild invited Hertzsprung to work with him in Göttingen, Germany, and the two of them moved later that year to the Potsdam Astrophysical Observatory. Hertzspring worked at the Leiden Observatory in the Netherlands from 1919 to 1944, finally retiring back in Denmark after his final nine years as direction of the observatory.