What is Ring galaxy?
{{one source|date=January 2021}} [[Image:Hoag's object.jpg|right|thumb|250px|Hoag's Object, a ring galaxy. Another red ring galaxy can be seen behind it, at the one o'clock podition]] A '''ring galaxy''' is a kind of galaxy that has a ring shape. [[Hoag's Object]] and [[NGC 1291]] are two examples.<ref name=APOD>{{Cite web|url=http://apod.nasa.gov/apod/ap020909.html|title=Hoag's Object: a strange ring galaxy|date=September 9, 2002|work=Astronomy Picture of the Day|publisher=[[NASA]] and Michigan Technological University|access-date=March 31, 2012}}</ref> The ring is made up of many massive, young blue stars, which are extremely bright. The middle of the galaxy contains far less luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because galaxies are mostly made up of empty space, a collision rarely happens between stars. However, the gravitational disruptions could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when an [[accretion disc]] is formed. Star formation would then result from the shocks and compressions in the newly formed disc. == References == {{reflist}} {{-}} {{science-stub}} [[Category:Ring galaxies| ]]