The Planet Factory: Exoplanets and the Search for a Second Earth

In the last few years, 3,500 planets have been confirmed to be orbiting stars outside the solar system, and 1,000 additional candidates have been identified. Tasker (solar system science, Hokkaido Univ., Japan) describes the theoretical formation of these extrasolar planets, or exoplanets, from dusty gas discs while also relating how exoplanets are detected. The Kepler space telescope, launched in 2009, has proven enormously successful at exoplanet detection, as it is more sensitive to the tiny dimming of stars than Earthbound observations. By combining these techniques, astrophysicists can determine the mass and radius of the exoplanet and gain a better sense of the nature of the planet itself: dense, rocky, or gaseous. The author explains how many planets are with either short or long orbits, extreme size or small mass, or possessing other qualities such as a reverse orbit or more than one sun. Inevitably, the question turns to the possibility of life on exoplanets. A brief glossary and suggestions for further reading conclude the work.