- NGC 7789 Caroline's Rose
NGC 6822 is a large, rich open cluster in the constellation Cassiopeia. It was discovered in 1783 by Caroline Herschell, the sister of William Herschell. Another name for this cluster is the "White Rose Cluster". These common names allude to the fact that, when viewed visually, the loops of stars and intervening dark lanes are reminiscent of the pattern of petals making up a rose blossom.
NGC 7789 lies at a distance of approximately 7600 LY. It has a visual magnitude of 6.7 and apparent diameter of around 16-25 arc-min (comparable to the size of the full moon). Its size and brightness make it an easy target for low-power telescopic viewing. This cluster contains around 600 member stars concentrated within an area around 50 LY across. NGC 7789 is an older cluster, with an estimated age of around 1.6 billion years. Because of this great age, most of the member stars have left the main sequence and entered the red giant stage. This accounts for the distinctive yellowish-orange color cast that the cluster exhibits (contrast it to the overall color of a young open cluster like M 11).
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