Vera Rubin: pioneer of dark matter
The American astronomer fundamentally advanced our knowledge of galactic dynamics, laid the groundwork for dark matter research, and was a lifelong advocate for women in science

To the point:
- Groundbreaking astronomer: Vera Cooper Rubin was one of the most influential scientists of the 20th century, fundamentally reshaping our understanding of galaxies and the cosmos.
- Pioneer of dark matter: Her measurements of galactic rotation curves revealed that stars orbit much faster than visible matter alone could explain—offering strong evidence for the existence of dark matter.
- Technical innovation: Rubin’s discoveries were made possible through precise optical spectroscopy, developed in collaboration with Kent Ford, to measure stellar velocities in galaxies like Andromeda and the Milky Way.
- Role model: A tireless champion of equality in science, Rubin worked to expand opportunities for women and inspired generations of young scientists through her mentorship and example.
Author: Helmut Hornung
There aren’t many major telescopes named after women. But one now gazes out into the universe from the highlands of northern Chile: the Vera C. Rubin Observatory. Equipped with an 8.4-metre mirror, this cutting-edge instrument is built to map the Milky Way, track near-Earth asteroids, and probe one of the universe’s greatest enigmas: dark matter. It’s a fitting mission for an observatory named after the astronomer who played a pivotal role in bringing this elusive substance into the scientific spotlight.
Vera Florence Cooper – later Rubin – began her journey into astronomy in childhood. By the early 1940s, at just twelve years old, she was already spending countless nights gazing at the sky, observing the Moon and planets, and tracing the fleeting paths of meteors. It was clear to Vera from a young age that she wanted to pursue astronomy.
Rubin earned a scholarship to Vassar College in New York, which was an all-women’s school at the time. During her summers, she worked as a research assistant at the Naval Research Laboratory in Washington, D.C. After graduating with honours in astronomy, she applied to Princeton’s graduate programme in 1948 –only to be rejected outright. The reason? She was a woman. Princeton didn’t admit women into its programmes then. The experience left a lasting impression on Rubin and fuelled her lifelong fight against gender discrimination in science and her advocacy for women’s equality in research.
But at just 20 years old, Rubin wasn’t about to give up. Instead, she found a new path at Cornell University, where she studied under some of the most respected physicists of the day, including Hans Bethe and Richard Feynman. It was also at Cornell that she met astronomer Martha Stahr Carpenter, who advised her on her master’s thesis on the velocity distribution of galaxies.
This research apparently impressed the head of the faculty at Cornell, who encouraged Rubin to present her findings at a meeting of the American Astronomical Society – on the condition that his name be included as a co-author. Rubin declined and decided to attend the conference alone. According to The Washington Post, her presentation was met with reactions that were “polite” but “persistent.” Yet, in a magazine article years later, Rubin offered a more candid account: many of the male astronomers in the audience, she recalled, responded with open anger and protest.
For her doctoral thesis at Georgetown University, Rubin studied the distribution of galaxies in space. Arrangements with her doctoral supervisor were challenging – his office was located in a part of the campus where women weren’t allowed. Despite these obstacles, Rubin persevered and made a key discovery: galaxies are not distributed evenly through space but tend to gather in clusters. After earning her PhD in 1954, she submitted her findings to the Astrophysical Journal for publication. But the editor-in-chief, Subrahmanyan Chandrasekhar – who would later win the Nobel Prize in Physics in 1983 – rejected the paper on the grounds that his own doctoral student was working on the same topic and his contribution should be published first.
After completing her doctorate, Rubin stayed on at Georgetown University for several years, conducting observational research at various observatories across the United States. Eventually, she was invited to the Mount Palomar Observatory in California, home at the time to the world’s largest telescope. Women were officially barred from the facility, with the lack of ladies’ toilets given as the reason. But the director made an exception for Rubin.
During her first stay, Rubin famously addressed issue by fashioning a makeshift skirt out of paper and taping it the restroom door marked “MEN,” declaring, “There you go; now you have a ladies’ room.”
In 1965, Rubin – by then a mother of four – accepted a part-time position at the Carnegie Institution in Washington. There, she met physicist Kent Ford, who had developed a highly sensitive image-tube spectrograph, perfect for measuring tiny shifts in spectral lines and, by extension, the velocities of stars. Rubin immediately saw its potential for her research on galaxies, especially in studying their so-called rotation curves.
It had long been known that galaxies – including our own Milky Way – rotate, with stars orbiting around their centres. The Sun, for example, completes one full orbit around the galaxy roughly every 230 million years. According to Newtonian physics, stars should slow down as they move farther from the centre of the Milky Way, much like planets in our solar system: Neptune, which is far from the Sun, moves more slowly than Mercury, which races close to the Sun. But until then, no one had ever measured the the rotational speed of another galaxy – one of the universe’s distant “island universes.” That changed with the work of Vera Rubin and Kent Ford.
They focused their attention on the Andromeda Galaxy, visible to the naked eye on clear autumn nights as a faint, blurry patch in its namesake constellation. During two observation sessions, they collected 123 spectra using the two-meter telescope at Lowell Observatory. Their study measured not only stars but also glowing gas clouds swirling around Andromeda’s core.
The astonishing result: all objects were moving at nearly the same speed, even at distances ranging from 10,000 to 60,000 light years from the galactic centre. These findings were consistent with a study Rubin had conducted with students in the early 1960s, which showed that stars in the Milky Way also moved at surprisingly constant speeds. As they studied other galaxies, Rubin and Ford found similar patterns. Though initially met with scepticism, their findings gradually gained acceptance: something unseen and mysterious was clearly affecting the motion of stars.
Rubin and Ford proposed that a vast amount of invisible material must exist in and around galaxies to account for such a dynamic effect and explain why stars maintain nearly uniform speeds. The two researchers had uncovered what would become known as dark matter. Today, we know it it makes up about 85 percent of all matter in the universe. Yet we still do not understand its nature.
Vera C. Rubin passed away on December 25, 2016, at the age of 88. In a field long dominated by men, she carved out her own path, confronting obstacles with quiet determination. Her perseverance helped lay the foundation for one of the most important discoveries in modern astronomy, one that continues to inspire and challenge scientists around the world.
Throughout her life, Rubin received numerous honours, including the Gold Medal of the Royal Astronomical Society and the Gruber Prize in Cosmology, where her role as a trailblazer and mentor to young women in science was especially highlighted. Despite her pioneering contributions, Rubin never received a Nobel Prize – an omission that, in hindsight, is widely regarded as a significant oversight.