Today is the birthday of German astronomer Johannes Kepler, who was the first astronomer to correctly pinpoint the laws of planetary motion, expanding on Copernican theory and leading to new fields of study. In his honor, NASA founded the Kepler mission, the search for terrestrial planets orbiting other stars. Over the past two year, the mission has identified more than 2,000 planet candidates, and, earlier this month, announced its first discovery of a planet, Kepler-22b, that is in the "habitable zone" of another sun, meaning that the temperature on that planet is though to be hospitable to life.
Below, some artists' renderings of Kepler's discoveries so far.
We want to hear what you think about this article. Submit a letter to the editor or write to firstname.lastname@example.org.