1000-world trouble

摘要

From a grand to a millennium, 1000 is an important milestone no matter what you are counting. But as astronomers close in on the discovery of 1000 exoplanets, deciding when to award the title is proving troublesome. For one thing, there are several exoplanet catalogues and each uses different criteria to decide when a planet has been spotted. As New Scientist went to press, the Extrasolar Planets Encyclopaedia, run by Jean Schneider of the Paris Observatory in France, listed 990 worlds: Schneider expects 10 more within a few weeks. But other exoplanet databases were coming up lower, including NASA's own, which had just 906.