Collinder 12

Collinder 12 is an open star cluster in the constellation Cassiopeia, also known as Cr 12 and NGC 457. It is much better known as the Owl Cluster, E.T. Cluster or Caldwell 13. It is a rich cluster of about 150 stars, roughly 7,900 light-years away, though estimates range from about 7,900 to 9,000 light-years. It stands out as the brightest open cluster in Cassiopeia, at magnitude 6.4. Two bright stars, Phi Cassiopeiae and HD 7902, form the "eyes" of the owl (or E.T.), with rows of fainter stars making up the wings or arms. Phi Cassiopeiae is probably a foreground star rather than a true member. The cluster is very young, about 21 million years old, and it was discovered by William Herschel in 1787.