What is Hoag’s Object?

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 galaxy is about 120,000 light-years wide, which is slightly larger than the Milky Way Galaxy. The gap separating the two stellar populations may contain some star clusters that are almost too faint to see. According to one school of thought, Hoag’s Object is a disk galaxy and the ring was formed from the end of a central bar that has since dissolved. Countering this is the view that the inner core is an E0 elliptical galaxy, not a disk, and that the ring resulted from an accretion event 2 to 3 billion years ago.  As rare as this type of galaxy is, oddly another ring galaxy can be seen, between the nucleus and the outer ring at the 1:00 position. Discovered in 1950 by astronomer Art Hoag, many of the details of the galaxy remain a mystery, foremost of which is how it formed. Some astronomers think it was a collision with another galaxy about 2 or 3 billion years ago but there is no sign of the second galaxy, which means the blue ring of stars may be the shredded remnants of a closely passing galaxy that were captured by the gravitational forces of the nucleic core.

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