Vera Rubin: the astronomer who uncovered dark matter

Astronomer Vera Rubin has changed the way we think about the universe by showing that galaxies are mostly dark matter.

On a dry, unobstructed night at the Kitt Peak Observatory, in the mountains of southern Arizona, Rubin closely observed the specter of stars in the Andromeda Galaxy to determine their speeds. The conditions of observation were perfect, if not for the heat that rises from the Sonoran desert. Rubin alternated between eating ice cream cones and developing exhibits that his colleague, Kent Ford, had just taken into the observatory. It was their first successful night in determining the speed of rotation of the stars of the galaxy around its center (what astronomers call the rotation curve). It was in 1968 and the movements of the galaxies were still a mystery.

"The surprises came very quickly," recalled Rubin years later in a written account of his life. "At the end of the first night, we were intrigued by the shape of the rotation curve."

The rotation curve was flat, which means that the stars in the outer spirals of the galaxy gravitated around the same speed as the stars near the center. More alarmingly, the stars in the outer spirals were in orbit so fast that they should have flown away. The mass of visible stars was not enough to keep the galaxy together. It lacked an extraordinary amount of material.

The Andromeda galaxy has become the first of a multitude of galaxies with inexplicable rotational curves, which Rubin has observed with Ford. Decades of Rubin's discoveries revealed that there was much more to the universe than we could see. The cosmos was packed black matter.

Discover the black

Swiss astronomer Fritz Zwicky for the first time proposed the existence of dark matter in 1933, after observing the movement of galaxies in the sky. Coma Cluster. The group of galaxies that he observed should have escaped if there was no extra mass keeping them together. In the absence of further evidence, his idea was quickly rejected by the scientific community.

Thanks in large part to Rubin's work, scientists now believe that only about 20% of the matter in the universe is visible. The remaining 80% is dark matter.

But what is dark matter?

"We do not know," said Regina Caputo, an astrophysicist at NASA's Goddard Space Flight Center. "We know what it is not, it's not a" normal "material like protons, neutrons, electrons or neutrinos – we know it's stable. that it is not loaded.We have a whole range of masses that it can be.But beyond that, we have not yet understood it. "

Inspired by Rubin, Caputo has spent most of his career trying to detect dark matter. It currently uses gamma ray observations from the Fermi gamma ray space telescope find signs of dark matter in the hearts of galaxies.

(Image: © NASA / Hubble)

The first years of Rubin

Rubin's affinities for astronomy started very early. She was born on July 23, 1928 to two Jewish immigrant parents who encouraged Rubin's scientific interests from the beginning. Her father helped her build a cardboard telescope, with which she photographed the movement of the stars. His mother persuaded the librarian to leave Rubin at the library of scientific books in the adult section of the local library. But it was especially Rubin's eternal curiosity that drove her.

"By the age of 12, I'd rather stay awake and watch the stars than go to sleep," Rubin said in a statement. interview with Alan Lightman in 1989. "I started learning." I started going to the library and reading, but initially I only looked at the stars in my room, nothing more interesting in my life than watching the stars every night. "

Her eagerness to learn has always overshadowed the loneliness she felt as a woman in the field of astronomy. according to American Museum of Natural HistoryRubin was the only student in astronomy in her 1948 class at Vassar College, a women's college in New York. When she tried to enroll in Princeton for graduate studies, they refused it because the astronomy program did not accept the students. Unperturbed, she attended Cornell University and Georgetown University for graduate studies.

(Image: © Linda Davidson / The Washington Post via Getty Images)

In Georgetown, she had to reconcile family and research. With one child to care for and another on the way, she began her doctoral studies taking classes in the evening. Her husband, Robert Rubin, would drive her to college, waiting in the car while studying.

Years later, she would become the first woman allowed to observe at the famous Palomar Observatory – the same observatory Fritz Zwicky had used to observe the Coma Cluster. Seeing that the only bathroom in the observatory was labeled "MEN", she drew a woman with a skirt and pasted it on the door.

Rubin's early research was largely rejected by his colleagues. His master's thesis on the large-scale movements of galaxies was controversial. His doctoral dissertation was largely ignored.

Wanting to avoid more competitive or more controversial areas of research, Rubin began his research on galaxy rotation. This brought Rubin to a permanent position at the Carnegie Institution in Washington DC, where she met and teamed up with Kent Ford.

Rubin's legacy

Rubin continued his research by revealing the presence of dark matter in many galaxies during the rest of his career. The growing amount of evidence from his research would make the case of dark matter undeniable.

In recognition of her contributions to astronomy, she was elected to the National Academy of Sciences in 1981. In 1993, President Bill Clinton awarded her the National Medal of Science. Although it has been neglected by the Nobel Committee, it has been and remains a source of inspiration for women scientists.

"I've really identified his difficulties in getting a permanent position," Caputo told Space.com. "She has bounced from one job to another for more than ten years.However, her struggle has inspired me to keep pushing, do what I love and truly believe that whatever It's going to work out, and now I'm a scientist at NASA. "

Rubin died on Christmas Day 2016, at the age of 88. It is commemorated in the solar system. Vera Rubin Ridge in the crater Gale on Mars and the asteroid 5726 Rubin were named in his honor. His four children have inherited his curiosity from the universe, each with a doctorate in science.

"My life has been an interesting journey," Rubin wrote in 2011. "I became an astronomer because I could not imagine living on Earth and not trying to understand the workings of the Universe."

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