NASA @NASA
Our galaxy contains billions of stars, our Sun among them. If each of those stars has not just one planet, but, like ours, a whole system, then the number of exoplanets (planets beyond our solar system) is truly astronomical: into the trillions. https://t.co/3T89p3cQXJ https://t.co/TswDFAFjvJ — PolitiTweet.org