Credit & Copyright: Tommy LeaseExplanation: Few star clusters this close to each other. Visible to the unaided eye from dark sky areas, it was cataloged in 130 BC by Greek astronomer Hipparchus. Some 7,000 light-years away, this pair of open star clusters is also an easy binocular target, a striking starfield in the northern constellation of the mythical Greek hero Perseus. Now known as h and chi Persei, or NGC 869 (above right) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun. In addition to being physically close together, the clusters' ages based on their individual stars are similar - evidence that both clusters were likely a product of the same star-forming region.
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Publications with keywords: open cluster
Publications with words: open cluster