It's an age-old question: are we alone? Or do other lifeforms and intelligences thrive on worlds far beyond our own? Ultra-sensitive telescopes and dogged detective work are transforming alien planet-hunting from science fiction into hard fact. Join NOVA on a visit to exotic worlds orbiting distant suns, from puffy planets with the density of Styrofoam to thousand-degree, broiling gas giants. Most tantalizing of all are the Super-Earths in the "Goldilocks zone," just the right distance from their sun to support life, and with one of them signaling life's essential ingredient, water, in its atmosphere. Are we on the brink of answering that haunting question?