6. Vera Rubin Astronomer (1928)
Vera Rubin was fascinated by the stars from a young age, building her own telescope with her fathers help, and attending meetings for young astronomers. She attended womens college, and graduated as the only astronomy major in 1948. There were astronomy classes at Princeton University, but they would not accept women onto their courses until 1975. Vera found a place at Cornell to study physics, and earned her PhD a few years later. She eventually began researching the galaxies, using a sensitive spectrometer that had been built by Kent Ford. She and Ford used the spectrometer to understand the light coming from the stars in different parts of spiral galaxies. Originally, astronomers had assumed that the core of a spiral galaxy was the location of most of the mass and gravity concentration, as that was where most stars were visible. In such a case, the further away a star is from the centre of the spiral galaxy, the slower its orbit was expected to be. However, when Vera and Kent began to research the orbital speeds in spiral galaxies, they were surprised. The stars the furthest from the centre were moving just as fast as the central stars. This meant that there must be a great amount of mass creating a gravitational pull in the outer regions of the galaxies but they couldnt see it. Veras calculations found that there must be 10 times as much dark invisible mass than visible stars. Vera realised that what she had found, was evidence for Fritz Zwickys theory of dark matter. Zwicky had realised that galaxies could not be held together by the gravity of their visible stars alone, and must contain dark matter to be held together. Her observations were so clear and straightforward that they defied argument. Luminous stars are only the visible traces of much larger masses within a galaxy. What dark matter is actually made up of is one of the scientific mysteries that have yet to be answered.