Explanation:
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
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