Pattern recognition software hasn't quite reached the shape-determining skill of the human brain, so Galaxy Zoo has enlisted over 200,000 volunteers to classify and describe some 66,000 or so galaxies from the massive Sloan Digital Sky Survey. (Our brains are almost too good at pattern recognition, as shown by one astronomer's observation of Lenin on his shower curtain.)
Astronomers, led by Karen Masters, found some striking results when they looked at a sample of over 13,000 galaxies that had been classified by Zooniverse volunteers. They found that there were significantly more bars in galaxies that were redder in color. Generally, as a galaxy stops forming stars, its overall colors change from blue to red as the most massive stars die off, leaving the mid-sized and small stars to dominate.
It is not clear whether the bars are instrumental in shutting off star formation or if they are a side effect of some other process that is related to the aging of a galaxy. Also, it has long been thought that bars help direct gas to the centers of galaxies, fueling star formation and supermassive black hole growth. As usual, the lives of galaxies are complicated and messy, however, huge samples and the dedicated work of many volunteers has added one more piece to the puzzle.
Image: Examples of SDSS galaxies. The one on the left is reddish and has a clear bar, whereas the blue spiral on the right does not. Credit: SDSS/Masters This research will be published in the Monthly Notices of the Royal Astronomical Society, and a preprint is available on arxiv.org.