Several collections of stars can be picked out in the sky, even with the naked eye. Closer study reveals that they really do form separate clusters in space. Such open star clusters are e.g. the Pleiades in Taurus and the Hyades around Aldebaran, the brightest star in Taurus. Almost the whole of the constellation Coma Berenices is also an open star cluster. Many objects appearing as nebulous patches to the unaided eye, when looked at with a telescope, turn out to be star clusters, like Praesepe in the constellation Cancer, or Misan, the double cluster in Perseus (Fig. 17.1). In addition to open clusters, some apparently nebulous objects are very dense globular clusters, such as those in Hercules and in Canes Venatici (Fig. 17.2).
KeywordsOpen Cluster Globular Cluster Main Sequence Proper Motion Cluster Member
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