Astronomers Calculate Comet's Orbit Using Amateur Images From The Web  - Technology Review

"For a short time back in October 2007, Comet 17P/Holmes became the largest object in the Solar System as the thin ball of dust and gas that surrounds it briefly became larger than the Sun. At the same time, Holmes brightened by a factor of half a million, making it visible to the naked eye....This sudden brightening triggered a huge wave of interest from astrophotographers all over the world, many of whom posted their images on the web. To find out how many, Dustin Lang from Princeton University in New Jersey and David Hogg at the Max-Planck-Institut fur Astronomie in Heidelberg, Germany, searched the web. They found 2476 different shots of Holmes. That's a significant astronomical database that represents a huge amount of work. But is it any use? Today, Lang and Hogg use these images to work out an accurate orbit of Comet 17P/Holmes, a significant achievement given that the data is taken from an ordinary web search and its provenance is entirely unknown...."