Hoag's Object is a rare, nearly perfectly symmetrical ring galaxy located about 600,000,000 light-years from Earth, discovered by astronomer Arthur Hoag. Its diameter is estimated at about 120,000 light-years, with this measurement referring primarily to the stellar ring itself rather than the “empty” space within it. The ring is composed mainly of young blue stars with active star formation, while the central region appears almost empty and contains only a very sparse population of older stars.

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