Are we alone? - NASA Science

Are we alone? - NASA Science: "Since the dawn of human civilization, humankind has looked to the stars and wondered if life, whether it be similar to our own or not, exists beyond our planet. Until 1992, when the first exoplanets were confirmed, it was uncertain whether there were even any planets outside of our own solar system. Today, thanks to the detailed data from the Astrophysics missions fleet, we now know of over 5,500 planets around other stars and thousands of other planet candidates. Of those confirmed exoplanets, roughly 50 small (roughly Earth-sized planets) orbit within their star’s habitable zone, where liquid water, which is essential for life as we know it, could potentially pool under the right conditions."