Maria Mitchell （1818 -1889）, the first woman astronomer （天文学家） in the United States, was born in Nantucket, Massachusetts. Her parents valued education and insisted on giving her the same quality of education that boys received.Her father, William Mitchell, was an astronomer and teacher himself. When he built his own school, Maria became a student and also a teaching assistant to him. At home, Maria' s father taught her to watch the stars and other natural objects in space using his personal telescope（望远镜）.Later she went to work at the library of the Nantucket Atheneum. Over the next twenty years, she further developed her interest in reading as many books as she could. She spent her nights watching the sky closely with her father.On October 1,1847 ,Mafia discovered a comet（彗星）by merely using a two-inch telescope. Some years before, King Frederick VI of Denmark had set up prizes to each discoverer of a "telescopic comet". The prize was to be given to the "first discoverer" of each such comet because comets were often discovered by more than one person.There was once a question of who should be the winner. As the story goes, Francesco de Vico had discovered the same comet two days later, but had reported it to the European official first. However, after some discussion this was settled in Mitchell's favor. She won the prize in 1848 and became a big name the world over. The comet was named "Miss Mitchell's Comet".What can be learnt about Mafia' s parents according to the text?