Establishing fundamental properties for Evolved Stars in Open Clusters

建立疏散星团中演化恒星的基本属性

• 批准号: 8292-2007
• 负责人: Turner, David
• 金额: $ 1.46万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=362742
• 关键词: Establishing; fundamental; properties; Evolved; Stars

It is possible to learn a lot about stars from the company they keep. Nowhere are such connections more obvious than in those beautiful stellar ensembles we call open clusters, groups of hundreds to thousands of stars sharing a common age, distance, and original chemical makeup. What makes open clusters of immense value is their ability to serve as mileposts indicating distance, luminosity, and evolutionary status for rare classes of objects that are found within them. For many years that has included Cepheid variables, pulsating stars about as hot as the Sun but orders of magnitude larger, that have evolved from stars roughly 3 to 30 times more massive than our Sun and that have consumed all of the hydrogen fuel available in their hot, dense cores. In 1975, lists of cluster Cepheids contained only about 10 objects, but that number currently exceeds 50, many newer additions arising from work by the applicant. Likewise, the number of planetary nebulae currently recognized to belong to open clusters is zero, or one at most, but that number might be 6 or more with a bit of focused effort. Planetary nebulae represent a stage of evolution beyond the Cepheid interlude, and they have a distance scale that is known much less reliably than that of Cepheids, even before Cepheids were recognized to be members of open clusters. Other exotic objects found in open clusters include massive, pulsating M supergiants, standard candles in their own right much like Cepheids, but also the last stage of evolution prior to their explosion as Type II supernovae. The common thread linking these various objects is that they represent advanced stages in stellar evolution, where our knowledge base is less secure. Perhaps we can learn more about such stages of stellar evolution from the examples located in open clusters.

我们可以从明星的朋友那里了解到很多关于他们的事情。这种联系在我们称之为疏散星团的美丽恒星群中最为明显，疏散星团由数百到数千颗恒星组成，它们有着共同的年龄、距离和原始化学组成。使疏散星团具有巨大价值的是它们作为里程碑的能力，表明了在疏散星团中发现的稀有天体的距离、光度和进化状态。多年来，造父变星是一种脉动恒星，它的温度和太阳差不多，但比太阳大几个数量级，它们是从质量大约是太阳3到30倍的恒星演化而来的，它们耗尽了炽热致密核心中所有可用的氢燃料。1975年，造父变星星团的列表中只有大约10个天体，但现在这个数字已经超过了50个，许多新的天体都是由申请人的工作增加的。同样，目前被认为属于疏散星团的行星状星云的数量是零，或者最多一个，但这个数字可能会增加到6个或更多。行星状星云代表了造父变星插曲之后的一个演化阶段，它们的距离尺度比造父变星的距离尺度更不可靠，甚至在造父变星被认为是疏散星团的成员之前。在疏散星团中发现的其他奇异物体包括巨大的、脉动的M超巨星，它们本身就像造父变星一样是标准的蜡烛，但也是在爆炸之前进化的最后阶段，即II型超新星。连接这些不同天体的共同点是，它们代表了恒星演化的高级阶段，在这个阶段，我们的知识库不太安全。也许我们可以从位于疏散星团中的例子中了解更多关于恒星演化的阶段。