- Person
- Vera Rubin
- Lived
- 1928–2016
- Field
- Astronomy
- From
- American
The story
Most people picture a spiral galaxy as a vast disc of stars all turning together in the same direction, like water circling a drain. For much of the twentieth century astronomers assumed the same: a galaxy was thought to have formed from a single rotating cloud, so all of its material should share one direction of spin. In the course of her long study of galaxy motions, Vera Rubin found that this is not always true.
Rubin spent decades at the Carnegie Institution's Department of Terrestrial Magnetism in Washington measuring how stars and gas move inside galaxies. She worked with spectrographs, instruments that spread a galaxy's light into its component colours so that tiny shifts in wavelength reveal whether material is moving towards or away from Earth, and how fast. By the late 1970s she had become one of the world's leading experts on galaxy rotation.
Her observations then revealed galaxies in which some of the gas and stars move in the opposite direction to the rotation of the rest. One striking example was NGC 4550, a galaxy in the Virgo cluster. In a 1992 paper in The Astrophysical Journal, Rubin and her colleagues J. A. Graham and J. D. P. Kenney reported that it contains two discs of stars occupying the same space but circling in opposite directions.
Such galaxies are hard to explain if each galaxy formed in one piece. They make much more sense if galaxies grow over time by absorbing smaller galaxies or clouds of gas that arrive from different directions, each bringing its own spin. Rubin's discovery of counter-rotation challenged the prevailing view that all material in a galaxy moves the same way, and it provided some of the first evidence for galaxy mergers and for the process by which galaxies are built up.
The finding came long after the work on flat rotation curves that made her famous, and it showed her lasting curiosity. She kept observing well into her later career, interested in every surprise the sky offered. Counter-rotating systems of the kind she studied remain valuable clues to how galaxies have been assembled over cosmic time.
Why it matters
Counter-rotating galaxies became important evidence for the modern picture in which galaxies grow over billions of years by merging with smaller systems and drawing in gas.
About Vera Rubin
Astronomer whose measurements of how galaxies spin gave the first persuasive evidence for dark matter, and a lifelong champion of women in science.
More about Vera Rubin
- Vera Rubin broke the barrier at Palomar ObservatoryIn 1965 Vera Rubin became the first woman permitted to observe at the Palomar Observatory, and when told it had no women's bathroom, she taped a paper skirt to the men's room sign.
- Vera Rubin saw that galaxies clump togetherIn her 1954 doctoral thesis under George Gamow, Vera Rubin concluded that galaxies clump together rather than being scattered randomly, an idea ignored for two decades before it became central.
- Vera Rubin found the evidence for dark matterMeasuring how fast stars orbit in spiral galaxies, Vera Rubin and Kent Ford found that the outer stars move far too fast, persuasive evidence that galaxies are held together by invisible dark matter.
- Vera Rubin was a lifelong champion of women in scienceVera Rubin campaigned for decades to open astronomy to women, saying it was well known that she was available twenty-four hours a day to women astronomers.
Sources
- Vera Rubin Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.