Focusing on Earth-like Planets

The Kepler mission has discovered more than a thousands planets around nearby stars, some of which are relatively close to the Earth in size. But determining whether these planets are truly Earth-like involved finding out much more about them, since Kepler images only tell astronomers the diameter of the planets it finds. Astronomers are now using ground-based telescopes to learn more about Kepler's finds, including their mass, which can tell them whether these planets are rocky, like the Earth, or fuzzy gas balls. Courtney Dressing, a graduate student at the Harvard Smithsonian Center for Astrophysics, and her colleagues, have found in their work that there seems to be a size cut-off for rocky planets. Anything more than 1.6 times the size of the Earth isn't a rocky planet, which means we can now focus on the smaller bodies to find a place more like home.