Hubble was able to resolve six variable stars in M31.

哈勃望远镜能分辨梅西叶云团表31中六颗变。

We also describe the basic principle of white dwarf cosmochronology and its application in defining the age of the Galactic disk, globular clusters, open clusters and Galactic halo.

介绍了白矮纪年学研究基本原理及其在银盘、球团、疏散团以及银晕年龄确定方面现。