The Extrasolar Planets Encyclopaedia

The Extrasolar Planets Encyclopaedia

How One Astronomer Became the Unofficial Exoplanet Record Keeper

astronomer Jean Schneider, maintainer of the online Extrasolar Planets Encyclopaedia

A RARE FIND: Hundreds of exoplanets have now been discovered and catalogued, but the planets orbiting the star HR 8799 are among the few that have been directly imaged. Image: GEMINI OBSERVATORY/NRC/AURA/C. MAROIS ET AL

In the past several days a number of news articles have touted the passage of a tidy astronomical milestone—the discovery of the 500th known planet outside the solar system. In the past 15 years, the count of those extrasolar worlds, or exoplanets, has climbed through single digits into the dozens and then into the hundreds. The pace of discovery is now so rapid that the catalogue of identified planets leaped from 400 to 500 entries in just over a year.

But the astronomer who tends to the exoplanet community's go-to catalogue tempered excitement surrounding the 500th-planet milestone in interviews and in an e-mail to fellow researchers, advising caution in assigning too much precision to the tally. Jean Schneider, an astronomer at the Paris Observatory, has since 1995 maintained The Extrasolar Planets Encyclopaedia, a modest-looking Web site that charts a wealth of data on known exoplanets as well as those that are unconfirmed or controversial.