The archaeology of galaxies in the local group

在过去的十年里，我（和我的研究团队）一直是哈勃太空望远镜的主要用户。我们已经非常成功地获得了大量的时间（在公开竞争中）来调查我们银河系中的一些古老的星团。研究的主要重点是确定这些系统的年龄，然后利用这些信息收集线索，了解银河系是何时以及如何形成的。我们已经开发了一种新的年龄测定技术，包括精确测量“死亡”恒星的冷却速度，并将其用作时钟。到目前为止，我们已经探索了银河系光晕中的两个星团，并确定它们的年龄大致相同，而且非常古老（120亿年）。由于我们非常确定宇宙本身只有137亿年的历史，我们现在知道我们的银河系（可能还有大多数其他星系）是在大爆炸后不久形成的。我们还把我们的天文钟应用到银河系的圆盘上，它包含着它宏伟的旋臂。在这里，我们了解到这个星系的组成部分要年轻得多——大约40亿年。目前，我们正在获取一组新的哈勃数据，这些数据是关于一个星团的，该星团包含的恒星与我们银河系中央凸起的恒星相似。这个星系的年龄将为我们的星系是由内向外（凸起较老）还是由外向内（凸起较年轻）形成提供证据。

Over the past decade I ( and my research team) have been major users of the Hubble Space Telescope. We have been extremely successful in obtaining very large amounts of time (in open competition) to survey a number of ancient star clusters in our Galaxy. The main focus of the research is to determine the ages of these systems and then use that information to glean clues as to when and how our Milky Way Galaxy was formed. We have developed a new age-dating technique that involves measuring precisely the cooling rate of "dead" stars and using this as a clock. Thus far we have explored two clusters in the halo of our Galaxy and have determined that both are about the same age and very old (12 billion years). Since we are quite sure that the Universe itself is only 13.7 billion years old, we now know that our Galaxy (and likely most others) formed rather soon after the Big Bang. We have also applied our chronometer to the disk of our Galaxy which contains its magnificent spiral arms. Here we learned that this Galactic component is significantly younger - by about 4 billion years. Currently we are in the process of obtaining a new set of Hubble data on a star cluster that contains stars similar to those in the central bulge of our Galaxy. An age for this system will provide evidence on whether our Galaxy formed inside out (bulge is older) or from the outside in (bulge is younger).