Asymmetry between galaxies with clockwise handedness and
  counterclockwise handedness
  While it is clear that spiral galaxies can have different handedness,
galaxies with clockwise patterns are assumed to be symmetric in all of their
other characteristics to galaxies with counterclockwise patterns. Here we use
data from SDSS DR7 to show that photometric data can distinguish between
clockwise and counterclockwise galaxies. Pattern recognition algorithms trained
and tested using the photometric data of a clean manually crafted dataset of
13,440 spiral galaxies with z<0.25 can predict the handedness of a spiral
galaxy in ~64% of the cases, significantly higher than mere chance accuracy of
50% (P<10^{-5}). Experiments with a different dataset of 10,281 automatically
classified galaxies showed similar results of $~65% classification accuracy,
suggesting that the observed asymmetry is consistent also in datasets annotated
in a fully automatic process, and without human intervention. That shows that
the photometric data collected by SDSS is sensitive to the handedness of the
galaxy. Also, analysis of the number of galaxies classified as clockwise and
counterclockwise by crowdsourcing shows that manual classification between
spiral and elliptical galaxies can be affected by the handedness of the galaxy,
and therefore galaxy morphology analyzed by citizen science campaigns might be
biased by the galaxy handedness. Code and data used in the experiment are
publicly available, and the experiment can be easily replicated.
