Astrobiology, the study of alien life, has long been a science without a subject. That may be about to change. The first exoplanet (a world orbiting another star) was discovered in 1992. Over 100 more are now known, and thousands of others that have been identified by space telescopes, such as nasa's now-defunct Kepler mission, await confirmation by instruments on Earth. Already several planets have been identified that are similar to Earth in terms of size, temperature and gravity. The statistics seem to suggest that Earth-like worlds are common in the galaxy. Estimates from the Kepler mission suggest that there may be 2 billion of them. The first detection of life on another planet could well happen within the coming century.
展开▼
