... Credit: Jose Suro Explanation: Located some 7,000 light-years away toward the constellation Perseus, this pair of open or galactic star clusters really is visible to the unaided eye and was cataloged in 130 BC by Greek astronomer Hipparchus . Now known as h and chi Persei (NGC 869/884), the clusters themselves are separated by a few hundred light-years and contain stars much younger, and hotter than the Sun. ... Publications with keywords: star cluster - galactic cluster . ...