Vera Rubin, the astronomer whose work first confirmed the existence of dark matter, has passed away at the age of 88. Along with that groundbreaking discovery, Rubin leaves a legacy of scientific achievements and awards, and was a strong advocate for women in science.

Dark matter, or at least the idea that some unseen force is affecting the mass of galaxies, had been theorized as early as the 1920s, but it wasn't until Rubin's work in the 1960s and 70s that its existence was confirmed. She and colleague Kent Ford were studying the distribution of mass in the Milky Way's nearest neighbor, the Andromeda galaxy, by observing how fast stars and gases orbit the galactic center at different distances.

But the orbits didn't line up with Newtonian gravitational theory, and after studying additional galaxies, the team determined that visible mass alone can't account for the stellar movements. A previously-unknown material was proposed, dubbed "dark matter" due to the fact that it doesn't emit, absorb or reflect light. This strange substance is believed to compose over 90 percent of the universe, and the search for the subatomic particle responsible continues to this day.

Apart from pioneering this field of research, Rubin leaves a legacy of helping to empower women to enter the male-dominated arenas of science. She was the first woman allowed to use the instruments at the Palomar Observatory, and she worked to increase the amount of women in bodies like the National Academy of Sciences (NAS) and academia in general.

"Vera was an amazing scientist and an amazing human being," says Neta Bahcall, a colleague of Rubin's from Princeton University. "A pioneering astronomer, the 'mother' of flat rotation curves and dark matter, a champion of women in science, a mentor and role model to generations of astronomers."

Vera Rubin was born July 23, 1928 and passed away December 25, 2016 in Princeton, New Jersey.