A ring galaxy is a ring-shaped galaxy, with much or most of
its brightness within a relatively-narrow ring some distance from
the center. The ring's typical bluish color indicates bright,
necessarily-young stars, suggesting a young age for the galaxy.
There is still discussion about their formation: they might result
from galaxy interaction (galaxy merger or tidal interaction
between passing galaxies) or from gas collisions in a manner to
trigger star formation in the a ring shape.