COUNTING AND CLASSIFYING MILLIONS OF GALAXIES. The Galaxy Zoo website (here) uses the efforts of thousands of nonscientists to make classifications of galaxies to select galaxies for further study. It started in July 2007, with a data set made up of a million galaxies imaged by the Sloan Digital Sky Survey. People were asked to make rough classifications of galaxies. Within 24 hours of launch they were receiving almost 70,000 classifications an hour. More than 50 million (!) classifications were received by the project during its first year, contributed by more than 150,000 people.
This page describes in more detail the first task for participants in 2007. Volunteers were asked to classify the galaxies into ellipticals, mergers and spirals and â€” if the galaxy was spiral â€” to record the direction of the arms. Multiple classifications were useful because they gave information on the accuracy of the classifications of a particular galaxy.
The linked page describes some of the uses of the millions of classifications, such as the comparison of galaxies now and in the past, to provide understanding of what factors influence their growth, “whether through mergers, active black holes or simply star formation.”