Every Soul a Star by Wendy Mass

Bree keeps a fashion notebook and dreams of life as a model. Ally is an amateur astronomer hoping to discover an exoplanet. Socially awkward Jack spends most of his time in a treehouse. All three find themselves in a camp in the middle of nowhere waiting for a solar eclipse. All three are on the verge of a big change in their lives. There are many insights into growing into being who you are as well as just how profoundly amazing the universe and all of its "stars" can be.