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Birthday · August 22, 2010

Hoag's Object: A Strange Ring Galaxy

August 22, 2010

Every candle on your cake is a tiny imitation of the stars that made you possible.

Hoag's Object: A Strange Ring Galaxy

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APOD published August 22, 2010. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.

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Hoag's Object: A Strange Ring Galaxy

Original APOD · August 22, 2010

Is this one galaxy or two? This question came to light in 1950 when astronomer Art Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag's Object formed remains unknown, although similar objects have now been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The above photo taken by the Hubble Space Telescope in July 2001 reveals unprecedented details of Hoag's Object and may yield a better understanding. Hoag's Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o'clock) is yet another ring galaxy that likely lies far in the distance.

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