(CNN) Vera Rubin, a pioneering astrophysicist who proved the existence of dark matter, had a gift for overcoming daunting challenges.

In the 1960s, she became the first woman to observe at the legendary Caltech's Palomar Observatory. But the boys club that ran the place had some bad news for her.

"They told her, 'It's a real problem because we don't have a ladies room,' so she went back to her room and took out a little piece of paper and cut it into a skirt and went to the bathroom door and stuck it on the men's figure on the door.

"She said, 'Look, now you have a ladies room.'"

"She could do anything of that nature, yet she was extremely kind and warm and positively, amazingly so," said Neta Bahcall, an astrophysicist who oversees Princeton's undergraduate astronomy program at 74 years old. "Vera never gave up on anything."

Rubin died on Sunday at the age of 88, the Carnegie Institution of Science said. Her colleagues and those who admired her spirit remember her as someone who revolutionized our understanding of the cosmos by confirming the existence of dark matter, invisible material that comprises more than 90% of the universe.

Rubin was "a national treasure as an accomplished astronomer and a wonderful role model for young scientists," said Carnegie president Matthew Scott. "We are very saddened by this loss."

A determined and brilliant start

Rubin was unstoppable, even from a young age. Stars fascinated her as a girl in the 1930s and '40s and her father helped her build a telescope, according to a profile of her on the American Museum of Natural History's web site. She went to the elite private school Vassar College on scholarship, graduating as the only astronomy major in 1948, it reads.

Princeton University did not accept women in its astronomy program, the profile says, so she attended Cornell University where she studied under legendary physicist Richard Feynman. She got a Ph.D. in 1954 at Georgetown University. She taught there for a decade.

In 1965, she landed at Carnegie's Department of Terrestrial Magnetism in Washington.

Rubin worked alongside colleague Kent Ford to study how stars orbit their galactic centers, and sought to figure the distribution of mass in the Andromeda galaxy, according to a piece about her life on Carnegie's site.

The two made a significant discovery , observing that gas and stars traveled at the same speed no matter whether they were near or far from the galactic center.

In the 1970s, Rubin and other astronomers found that invisible mass was responsible for the stars' movement, determining that each spiral galaxy has a halo of dark matter, or material that doesn't give off light and goes beyond what one can see in the galaxy, according to Carnegie. While there were indications going back to the 1930s that dark matter existed, her work confirmed it.

As Rubin achieved professionally, she continuously reminded colleagues that she wasn't the only capable female scientist.

Bahcall said her friend inspired, mentored and pushed for opportunities for women where none existed.

A colleague who had just started an astronomy tract at the University of Chicago asked Rubin to advertise it. She sent him a note saying that if she were a promising young scientist she would never apply there because the program had no women on its faculty.

Rubin also advocated for women to be included in Princeton's private social salon, the Cosmos Club.

"She fought them until they finally allowed women," Bahcall said, managing to avoid stoking anyone's ire too much. "She did it all in a very good-natured way. It was very difficult to be mad at her."

Carnegie honored her in 2002 where a slide show featured some of her wisdom.

"I live and work with three basic assumptions," Rubin wrote.

"1) There is no problem in science that can be solved by a man that cannot be solved by a woman.

"2) Worldwide, half of all brains are in women.

"3) We all need permission to do science, but, for reasons that are deeply ingrained in history, this permission is more often given to men than to women."

Accolades but not the Nobel

Rubin racked up many top prizes in her field. According to various biographies, she was elected to the National Academy of Sciences in 1981. In 1993, she received the National Medal of Science, the country's highest scientific prize. In 1996, she became the first woman since 1928 to receive the Royal Astronomical Society's Gold Medal.

She lost her husband, mathematician and physicist, Robert J. Rubin, in 2008. They had four children who were as ambitious and smart as their parents. Each acquired Ph.D.s in math or science, according to Carnegie.

There was controversy in recent years about the Nobel committee passing on awarding a prize to Rubin.

Emily Levesque, an astronomer at the University of Washington in Seattle has said, "The existence of dark matter has utterly revolutionized our concept of the universe and our entire field; the ongoing effort to understand the role of dark matter has basically spawned entire subfields within astrophysics and particle physics at this point. Alfred Nobel's will describes the physics prize as recognizing 'the most important discovery' within the field of physics. If dark matter doesn't fit that description, I don't know what does."

Bahcall said that her friend "really did not pay much attention to that" and not winning a Nobel prize "didn't bother her."

"She was enormously happy with her work," Bahcall said.

Others worked on the subject of dark matter, and it's important to remember that in science, each person's achievements are built on the backs of those who came before.

It's a truth to remember, especially when honoring the life of a scientist and woman like Rubin.