Shockingly, Carroll notes that if our own Earth had formed just one percent farther away from the Sun, it would have suffered a runaway glaciation. By contrast, one percent further in and Earth would have suffered a runaway greenhouse and the fate that befell present-day Venus. “The habitable zone is a planetary tightrope,” writes Carroll.

However, the book does cover the possibility that super-earths and/or gas giant planets that lie in their parent stars’ habitable zones might also harbor planet-sized moons. As the book notes, it’s an idea that Hollywood director James Cameron’s embraced in his ground-breaking movie “Avatar.”

“Envisioning Exoplanets” also offers the reader capsule summaries of the various detection techniques that astronomers have used through the years to remotely explore and characterize these far-flung worlds.