Galaxy Zoo is a crowdsourced astronomy project which invites people to assist in the morphological classification of large numbers of galaxies. It is an example of citizen science as it enlists the help of members of the public to help in scientific research.
Galaxy Zoo
ARCSAT and SDSS telescope buildings at the Apache Point Observatory
CW or ACW? This HST image of Messier 101, the Pinwheel galaxy has it in its normal S-wise orientation and then reversed.
HST image of NGC 3314, an example of an overlapping galaxy.
Galaxy morphological classification
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by GĂ©rard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology.
Spiral galaxy UGC 12591 is classified as an S0/Sa galaxy.
The Hubble sequence throughout the universe's history
NGC 6782: a spiral galaxy (type SB(r)0/a) with three rings of different radii, as well as a bar.
NGC 7793: a spiral galaxy of type SA(s)d.