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Birthday · December 23, 2008

Collinder 399: The Coat Hanger

December 23, 2008

When you were born, the Sun rose on a world that had never seen you before. Since then, every dawn has arrived in a universe subtly altered...

Collinder 399: The Coat Hanger

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APOD published December 23, 2008. Credit: Noel Carboni. A publication-date match, not a photo taken on your date. Independent of NASA.

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Collinder 399: The Coat Hanger

Original APOD · December 23, 2008

Is this coat hanger a star cluster or an asterism? This cosmic hang-up has been debated over much of last century, as astronomers wondered whether this binocular-visible object is really a physically associated open cluster or a chance projection. Chance star projections are known as asterisms, an example of which is the popular Big Dipper. Recent precise measurements from different vantage points in the Earth's orbit around the Sun have uncovered discrepant angular shifts indicating that the Coat Hanger is better described as an asterism. Known more formally as Collinder 399, this bright stellar grouping is wider than the full moon and lies in the constellation of the Fox (Vulpecula). On the far right of the image is the open cluster of stars NGC 6802. Note : APOD Editor to Speak in New York on Jan. 2

Image credit: Noel Carboni

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