Do We Live in the Rarest Solar System In The Universe? We're about to find out!

There are lots of reasons to search for planets around other stars—exoplanets. A big one is to find other places in the universe that might harbor life. We only know of one such planet so far: Earth. And so we get particularly excited when we find Earth-mass planets at the right distance from their star to sustain liquid water—also critical for life as we know it. We’ve found lots of those “habitable” wo rlds. But we also don’t know what factors are really critical to the initial development of life.