Sandra Stark's List: Networks

A Dutch schoolteacher with no formal training in astronomy, Ms. van Arkel had joined tens of thousands of other Web volunteers to help classify photographs taken by deep-space telescopes. Stumped by the unusual image on her computer screen, she e-mailed the project staff for guidance. Staff members were stumped, too. And thus was christened the celestial body now known to astronomers worldwide as Hanny’s Voorwerp (Dutch for “object”).

Stories like Ms. van Arkel’s are becoming more common, as the Internet opens up new opportunities for so-called citizen scientists. And as millions of people get involved in these participatory projects, scientists are grappling with how best to harness the amateurs’ enthusiasm.