The Oldest Open Star Clusters Revisited: Their Distances, Reddenings and Ages

重访最古老的疏散星团：它们的距离、红化和年龄

• 批准号: 9731656
• 负责人: Kenneth Janes
• 金额: --
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9731656&HistoricalAwards=false
• 关键词: Oldest; Open; Star; Clusters; Revisited

AST 97-31656 Kenneth Janes Dr. Janes is observing five nearby open star clusters with approximate ages greater than 2,000,000,000 years. The goal of the project is to determine the fundamental properties, particularly the ages, of stars in these five open clusters. Perhaps the greatest uncertainties in the ages of star clusters are the uncertainty in the distance scale and the difficulty in determining interstellar reddening. The distance scale (from the nearest stars to the edge of the Universe) depends and builds upon the fundamental determination of stellar parallax. The availability of the new Hipparcos Catalog with its precise parallaxes makes it possible to resolve some of these uncertainties - especially for open clusters. Because there are large numbers of nearby Population I main-sequence stars, many of which have better determined parallaxes than the subdwarfs, and because the standard star color systems are defined by many of those same parallax stars, it is possible to do a better job of tying the old open cluster distance scale to the Hipparcos than can be done with globular clusters. The PI is obtaining new high precision photometry of these five clusters, and also developing improved analysis tools to reduce the data. The five clusters span the age of the Milky Way disk, so they are well matched to the problem. The project depends upon large numbers of observations on moderate aperture telescopes combined with careful and extensive calibrations. Regular photometric monitoring of open cluster stars will make it possible to identify many, if not most, of the non-member stars, as well as variable stars and binaries. Other interesting stellar phenomena might be found and characterized: delta Scuti stars, reflection effects in close (but non-eclipsing) systems, and eclipsing systems with secondary components perhaps as small as Jupiter. ***

Kenneth james博士正在观测附近的五个年龄大约大于20亿年的疏散星团。该项目的目标是确定这五个疏散星团中恒星的基本属性，特别是年龄。也许星团年龄最大的不确定性是距离尺度的不确定性和确定星际变红的困难。距离尺度（从最近的恒星到宇宙边缘）取决于并建立在恒星视差的基本决定之上。新Hipparcos星表的精确视差使得解决这些不确定性成为可能——特别是对于疏散星团。因为附近有大量的星族I主序星，其中许多星族I主序星比亚矮星有更好的视差，而且因为标准恒星的颜色系统是由许多相同视差的恒星定义的，所以将旧疏散星团的距离尺度与喜巴谷星团联系起来可能比用球状星团做得更好。PI正在获得这五个星团的高精度光度测量方法，并开发改进的分析工具来减少数据。这五个星团跨越了银河系盘的年龄，所以它们很好地匹配了这个问题。该项目依赖于中等口径望远镜的大量观测，并结合仔细和广泛的校准。定期对疏散星团的恒星进行光度监测，将有可能识别出许多（如果不是大多数的话）非成员星，以及变星和双星。其他有趣的恒星现象可能会被发现并被描述：三角天牛星，近距离（但非食）系统的反射效应，以及具有次要成分的食系统，可能像木星一样小。＊＊＊