Within this use case you discover the shapes of galaxies and their
classification according to the Hubble diagram. You are offered
sequences of galaxies with different morphologies and are asked to
order them. The morphological classification of galaxies is still in
use even if we have discovered that the Hubble diagram "per se" has no
direct physical or evolutionary meaning. Besides introducing the main
shapes of galaxies, the use case offer a demonstration of the
classification process, a fundamental tool of astronomers.
