Marie Mitchell was the first American woman astronomer. On the night of October 1, 1847, Mitchell stood on a Nantucket rooftop with her telescope and discovered a telescopic comet, which is invisible to the naked eye. This discovery gave her worldwide fame since she was only the second woman to see a comet (the first being German-British astronomer Caroline Herschel). In 1865, she become the first astronomy professor, male or female, at Vassar College. In addition to being an advocate in the Woman’s Rights movement, Mitchell was the first woman elected to the American Academy of Arts and Sciences.