Maria Celeste was the daughter of Galileo Galilei and Marina Gamba. She was entered into the San Matteo convent after her thirteenth birthday. Her original name was Virginia, but she changed it to Maria Celeste in honor of the virgin Mary and her father's love for astronomy. Although Maria Celeste was confined inside the walls of the convent at San Matteo for the rest of her life, she remained as a constant source of support for her father.

Ultimately, she was the one who kept Galileo alive and healthy. She took care of him by providing him with food and shelter. Maria did his laundry and shopping. Not only that, she made sure that her father didn't drink too much or overwork himself. Maria sent her father herbal medicines, she made herself, for his various sicknesses. For instance, during the time of the Bubonic plague in 1630, Maria put together medicine for her father to help him defend himself against the disease. Despite being away, Maria never lost her sense of being a dutiful Italian daughter and was constantly worried about her father's health and well-being.

Maria Celeste also assisted Galileo in other things besides keeping him healthy. While Galileo was writing his book The Dialogo, letters were being sent back and forth between Maria and him. She was essentially the editor of The Dialogo. She read the unfinished manuscript and edited it so it can be published. She cut and took out pieces of information that was irrelevant as well as put information that was missing/needed. The mistakes and the needed information her father forgot as well as advice about the book was sent back forth between them in their letters. She prepared the manuscript of Galileo's book so that it could be published and be acceptable to the church. She was able to do this since she was nun. She knew what pieces of the book would go against the church, and thus would not let the book be published. Therefore, without her, Galileo's book probably would have not been the way it is and maybe even couldn't be published.

After Galileo published his book, Pope Urban VIII took a very angry view of the book and two, former friends, never spoke with each other again. Galileo then had to appear before the Inquisition because of his book. Before appearing on trial, Maria Celeste heard about the news and wrote to her father, giving him advice on how to stay alive and avoid the grossum punishments. She advised him to say what they want you to say and to do what they tell him to do. She warned him not to say anything that would go against or anger the Church. Because of Maria's advise, Galileo was able to stay alive and begin his studies on physics.

Despite the fact Maria did not receive formal education or training, she was a very intelligent woman who assisted her father in his scientific discoveries greatly by keeping him alive and editing his book's manuscript.