Among Trillions of Planets, Are We 'Home Alone?'
Among Trillions of Planets, Are We 'Home Alone?' By Pat Brennan NASA's Exoplanet Exploration Program Once seen as the center of the universe, Earth has suffered a series of demotions over the past few hundred years. Now, in an age of fast-paced discovery, we’ve learned we’re likely just one of trillions of planets in the Milky Way galaxy – and among the smaller ones at that. If, from Earth's surface, we could see the very distant exoplanets – planets around other stars – that have been discovered so far, as in this fanciful illustration, they would show a stunning variety of sizes and types. But none, so far, has revealed any indication of life. Illustration: NASA/JPL-Caltech/Lizbeth B. De La Torre Yet Earth remains a standout, and so far, one of a kind. Of the thousands of exoplanets – planets around other stars – confirmed by our increasingly powerful telescopes, and despite extensive probing of the solar system, ours is still the only planet known to host life. In s