The year 1609 was noteworthy for two astronomical milestones. That was when Galileo built his first telescopes and began his meticulous study of the skies. Within months he discovered the four major satellites of Jupiter, saw that Venus (like our moon) has illuminated phases and confirmed earlier observations of sunspots — all evidence that undermined the Aristotelian model of an unchanging, Earth-centered cosmos. During that same year, Johannes Kepler published Astronomia Nova, which contained his detailed calculation of the orbit of Mars. It also established the first two laws of planetary motion: that planets follow elliptical orbits, with the sun at one focus, and that planets sweep through equal areas of their orbits in a given interval. Small wonder, then, that when the United Nations General Assembly declared an International Year of Astronomy to promote the wider appreciation of the science, it selected 2009, the quadricentennial of those standout accomplishments (among many) by Galileo and Kepler that informally founded modern astronomy. Currently astronomers can look beyond the familiar planets and moons to entirely new systems of worlds around other stars. As I write this, the tally stands at 344 known extrasolar planets. Only a handful of these bodies were found by telescopic means that Galileo or Kepler would have recognized, but each one owes its discovery to their work. A recent and surprising trend is the apparent abundance of planets turning up close to very small stars — suns that may not be much larger than the planets circling them. Astronomers Michael W. Werner and Michael A. Jura have written on why the existence of these unlikely planetary systems might imply that the universe is chock-full of planets. This year also marks the 50th anniversary of the famous "Two Cultures" lecture by C. P. Snow, the English physicist and novelist. Snow"s speech, and his later books that elaborated on it, argued that communication and respect between the sciences and humanities had broken down. Literary intellectuals, he said, were often confused at their own ignorance of basic science and yet would be shocked at a scientist unfamiliar with Shakespeare; conversely, scientists were more likely to have some schooling in the arts. This asymmetrical hostility hurt society, Snow maintained, because it hindered the embrace of what science and technology could do to eliminate poverty and inequality. Even today critics disagree about whether Snow"s thesis is better seen as controversial or clichéd. If the "two cultures" is a problem, however, some leaders — not just in science but also industry, government and nongovernmental organizations — are overcoming it spectacularly. They are doing what they can to ensure that the fruits of scientific knowledge are constructively applied to improve well-being and prosperity. This month, with our Scientific American 10 honor roll, we are proud to recognize a few of them.