Then the day came when Caroline was offered a contract to sing professionally. At last, her musical future seemed assured. Finally, she would be able to support herself. But now she had a difficult choice to make.

   William’s enthusiasm for astronomy was eating into his time. Every night he gobbled down his dinner. Then he rushed off to study physics or astronomy. When not closeted with books, he designed telescopes. Or he spent hours observing the night sky. Then he started building and selling telescopes as well.

   Caroline loved her brother and knew she owed her freedom to him. She also knew he needed her help if he was to have time to study astronomy, carry out his observations, and build bigger and better telescopes. Many years later, she wrote, “My brother would have been very much at a loss but for my assistance.” She gave up her chance at a musical career and devoted herself to helping William revolutionize astronomy.

   Caroline may have been a tiny person, but she was a dynamo. She loved astronomy and threw herself into telescope building. “I saw almost every room turned into a workshop,” she wrote. “A cabinet maker making tubes and stands of all descriptions in a handsome furnished drawing-room. Alex putting up a huge turning machine in a bedroom for turning patterns, grinding glasses and turning eye-pieces.”

   The Herschels set out to transform the science of astronomy. First, they built telescopes that were bigger and better than any the world had known. Then, they used their telescopes to study the night sky in a completely new way. Caroline wrote, “William wanted to study the construction of the heavens. He was not content knowing what other observers had seen.” Caroline became the recorder. As they scanned the sky systematically, she carefully entered all their data in her journals. In 1779, they began an ambitious project. They planned to identify and map every single object they saw in the night sky. In three years, they swept the sky three times. A sweep requires looking at every portion of the sky and recording the locations and times of appearance of all objects. In their first full sweep, they discovered the planet Uranus, the first new planet to be found in a thousand years.