Twinkle, Twinkle, Little Star I know exactly what you are. Opaque ball of hot dense gas, million times our planet's mass, looking small because you're far I know exactly what you are Written by an expert in astrophysics, this book is the perfect primer for learning exactly what those twinkling little stars are doing way up high in the sky. Each stanza explains what stars are made of and their relationship to the earth in an easy-to-understand way.