The collection of amateur astro photos posted on the internet could make up a vast untapped sky survey to rival even professional telescopes. A new study uses photos culled from an online image search to reconstruct the orbit of a comet.

“This is one area where groups of amateur astronomers — distributed, diverse, and taking images at rapid cadence and with good time resolution — can contribute data that are complementary to what the big telescopes produce,” astronomer Dustin Lang of Princeton University told Wired.com in an e-mail. “We’re thinking about what we could discover if we could slu...