Ring galaxies turn out to be much more common than was believed.

A ring galaxy is a galaxy with a circle-like appearance.

Hoag's Object is a non-typical galaxy of the type known as a ring galaxy.

Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy.

A ring galaxy is thought to occur when a smaller galaxy passes through the core of a spiral galaxy.

So-called "classic" ring galaxies are generally formed by the collision of a small galaxy with a larger disk-shaped galaxy.

As noted above, these ring galaxies may have formed when a companion galaxy passed through the ring galaxy.

An example of this is the ring galaxy, which possesses a ring-like structure of stars and interstellar medium surrounding a bare core.

A nearly perfect ring of young hot blue stars circles the older yellow nucleus of this ring galaxy 600 million light-years away in the constellation Serpens.

The Cartwheel Galaxy (also known as ESO 350-40) is a lenticular galaxy and ring galaxy about 500 million light-years away in the constellation Sculptor.

In 1998, images from the European Space Agency's Infrared Space Observatory demonstrated that the overall form of the Andromeda Galaxy may be transitioning into a ring galaxy.

NGC 1291, also known as NGC 1269, is a ring galaxy with an unusual inner bar and outer ring structure located about 33 million light-years away in the constellation Eridanus.

Over the years, Iowa State researchers have used the Fick Observatory for a wide variety of studies, including stellar radial velocity observations, studies of ring galaxy collisions, and lunar occultation studies.

Galaxy Zoo 2 allows for a much more detailed classification, by shape and by the intensity or dimness of the galactic core, and with a special section for oddities like mergers or ring galaxies.

As rare as this type of galaxy is, another more distant currently unnamed ring galaxy can be seen through Hoag's Object, between the nucleus and the outer ring of the galaxy, at roughly the one o'clock position in the picture to the right.

His specialty included reanalyzing Hubble and Sandage's galaxy atlas and recomputing the distance measurements utilizing a method of averaging many different kinds of metrics such as luminosity, the diameters of ring galaxies, brightest star clusters, etc., in a method he called "spreading the risks."