Ring Galaxy

A ring galaxy is a galaxy with a circle-like appearance. Hoag's Object, discovered by Art Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.

Other articles related to "ring, ring galaxy, galaxy":

Hoag's Object - Characteristics
... 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 6″ (seconds of arc) inner core of the galaxy is about 17±0.7 kly (5.3±0.2 kpc) while the surrounding ring has an inner 28″ diameter of 75±3 kly (24.8±1.1 kpc) and an ... 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 1205 ...

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