Libby was born with a heart three sizes too big. She takes daily shots, can’t do monkey bars, and doesn’t always read social cues. But having Turner Syndrome doesn’t mean she can’t be a scientist when she grows up. Besides her big sister Nonny, Libby’s hero is astronomer Cecilia Payne, who discovered what stars are made of. When Nonny comes home to stay and tells Libby that she and her husband Thomas are having a baby, Libby knows what to do: She’ll make Cecilia Payne the subject of her entry into a contest, and give all the first-place prize money-twenty-five thousand dollars!-to Nonny’s growing family. But it’ll take more tenacity than she’s ever needed to help take care of the sister who has always taken care of her, all while navigating middle school with a unique set of challenges.