One recent study suggests that they are two star clumps within a single open cluster (which astronomers would designate as NGC 1817). Another provides evidence that NGC 1807 is not a cluster at all, but a chance grouping of unrelated stars in the same region.
A surprise in Cassiopeia?
Cassiopeia has several open clusters of interest. One of its more fashionable ones is M103, which lies 1° east-northeast of Ruchbah. Several other galactic clusters also populate that region, three of which form a popular open cluster arc about 1½° farther to the east: NGC 654, NGC 659, and NGC 663.
Despite the close proximity of NGC 663 to NGC 659 (a scant 36'), these clusters have no relation to each other. The twist is that NGC 659 not only has much in common with NGC 654 (including its distance), but it is also a near twin of M103: Both lie about 8,000 light-years distant, measure 6' in apparent diameter, shine around 8th magnitude, contain some 180 members across 15 light-years of space, and have ages between 20 and 25 million years!
The night sky is full of wonderful surprises, sometimes two at once. As always, enjoy the views and send your thoughts to
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