““Since 1995, astronomers have found nearly two thousand confirmed planets around other stars. Some of these planets are similar to Earth in size and mass. About two dozen of them orbit in the habitable zone, the distance from their stars where temperatures are potentially suitable to our kind of life. Extrapolating broadly, there may be 50 billion habitable planets in our galaxy. Nowadays, there is an entire field of science known as astrobiology—the study of life among the stars.””
