The first comet to be discovered by telescope was spotted 151 years ago today by Maria Mitchell (1818-1889), the first well-known woman astronomer in the United States. While working as a librarian, Mitchell spent her nights sweeping the sky with a 4-inch telescope on the roof of her father's home. In 1847, she spotted a comet. The 29-year-old Mitchell received a gold medal from the King of Denmark, who 16 years earlier had offered the award for the first discovery of a comet not visible to the naked eye. Soon thereafter she started working for the U.S. Nautical Almanac Office, computing the positions in the sky of the planet Venus. From 1865 to 1888 Mitchell served as professor of astronomy and director of the college observatory at Vassar Female College, where she used the nation's third-largest telescope (12 inches) for her research.
[Source: Charles Coulston Gillespie, Ed., Dictionary of Scientific Biography (Charles Scribner's Sons, New York, 1973).]