A CCD Survey For Old White Dwarf Stars

由于白矮星的冷却时间非常长，银河系中最古老的恒星还没有褪色到探测极限以下。因此，白矮星的光度函数应该显示出一个突然的下降，低于它们在进化过程中可能达到的亮度。这个事实可以用来确定年龄。不幸的是，所讨论的恒星都很微弱，而且在星系盘中发现的恒星数量太少，无法提供一个好的统计样本。即使有，在光环中也很少有人知道。德克萨斯州麦克唐纳天文台30英寸望远镜上的CCD相机将被用来在圆盘群和光晕中寻找凉爽、微弱的白矮星。这将大大增加已知的这类恒星的样本，并将使它们对研究它们所代表的恒星群的恒星形成历史和年龄更有用。

Because the cooling times for white dwarfs are very long, the oldest stars in the galaxy have not yet faded below detection limits. Thus, the white dwarf luminosity function should show a sudden drop-off below the luminosity they could have reached in the age of the population from which they evolved. This fact can be used to determine that age. Unfortunately, the stars in question are faint and the numbers found in the galactic disk are too small to provide a good statistical sample. Few, if any, are known in the halo. A CCD camera on the McDonald Observatory 30 inch telescope in Texas will be employed to search for cool, faint white dwarfs in both the disk population and the halo. This will increase greatly the sample of such stars known and will make them much more useful for studying the star formation history and age of the populations they represent.