NGC 7789 is an open cluster

Open cluster

An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 in Cassiopeia that was discovered by Caroline Herschel

Caroline Herschel

Caroline Lucretia Herschel was a German-British astronomer, the sister of astronomer Sir Friedrich Wilhelm Herschel with whom she worked throughout both of their careers. Her most significant contribution to astronomy was the discovery of several comets and in particular the periodic comet...

 in 1783. Her brother William Herschel

William Herschel

Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

included it in his catalog as H VI.30. This cluster is also known as "The White Rose" Cluster or "Caroline's Rose" Cluster because when seen visually, the loops of stars and dark lanes look like the swirling pattern of rose petals as seen from above.