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August 18, 2017

Researchers publish catalog of galaxies (Image 5)

This galaxy is NGC 3615 and was identified as an elliptical galaxy by the Galaxy Zoo 2 project (Willett et al. 2013). Elliptical galaxies generally have smooth light profiles with no spiral arms. Most elliptical galaxies contain older stars and have less gas than their spiral counterparts. [Image 5 of 6 related images. See Image 6.]

More about this image
Galaxy Zoo 2 is the second phase of a crowdsourcing effort to categorize galaxies in our universe.

Researchers already know computers are good at automatically measuring the properties -- such as size and color -- of galaxies but more challenging characteristics, such as shape and structure, can currently only be determined by the human eye. So, between February 2009 and April 2010, more than 83,000 Galaxy Zoo 2 volunteers from around the world looked at images online, gathered from the Sloan Digital Sky Survey. They answered questions about different galaxies, including whether they had spirals, the number of spiral arms present, or if they had galactic bars -- long, extended features that represent a concentration of stars. Each image was classified an average of 40-45 times to ensure accuracy. More than 16 million classifications of more than 300,000 galaxies were gathered representing about 57 million computer clicks.

Next, an international group of researchers, led by the University of Minnesota, produced a catalog of the new galaxy data. The catalog is 10 times larger than any previous catalog of its kind and is available online at

The National Science Foundation (NSF) provided funding for both the Sloan Digital Sky Survey, to gather the images, and the Galaxy Zoo project, to categorize them (NSF grants DRL 09-41610 and AST 08-02876).(Date image taken: 2009-2010; date originally posted to NSF Multimedia Gallery: Aug. 18, 2017)

Credit: Sloan Digital Sky Survey (SDSS) Collaboration/

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