ESO091207：类太阳恒星的亮度变化之谜更深了

http://www.eso.org/public/outreach/press-rel/pr-2009/pr-48-09.html

ESO 48/09 - Science Release
07 December 2009
For immediate release
ESO2009年第48#公开新闻，科学类，2009.12.9即时公布。
Brightness Variations of Sun-like Stars: The Mystery Deepens
类太阳恒星的亮度变化之谜更深了
Astronomers facing Socratic “ignorance”
天文学家面临苏格拉底所谓的"无知"窘境

                               
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Anextensive study made with ESO’s Very Large Telescope deepens a long-standingmystery in the study of stars similar to the Sun. Unusual year-long variationsin the brightness of about one third of all Sun-like stars during the latterstages of their lives still remain unexplained. Over the past few decades, astronomershave offered many possible explanations, but the new, painstaking observationscontradict them all and only deepen the mystery. The search for a suitableinterpretation is on.
ESO使用甚大望远镜（VLT）对一个长期存在的谜进行了广泛的研究：大约1/3的类太阳恒星在其生命的后期，具有为期约一年的光度变化，原因不明。在过去数十年，天文学家提供了很多可能的解释，但是新的辛勤观测否定所有解释，却更加深了这个谜。适当的解释还在寻找中。

http://www.eso.org/gallery/d/219656-3/phot-48a-09-fullres.tif, 6500x4592, Credit: ESO/S. Steinhöfel  Full Size Original：49667 kB

                               
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“Astronomers are left in the dark, and for once, we do not enjoy it,” says Christine Nicholls from Mount Stromlo Observatory, Australia, lead author of a paper reporting the study. “We have obtained the most comprehensive set of observations to date for this class of Sun-like stars, and they clearly show that all the possible explanations for their unusual behaviour just fail.”
本报告的首席作者，澳洲史创罗峰天文台的Christine Nicholls说：“天文学家被留在黑暗中了，但这次，我们并不喜欢。我们对这种类太阳恒星进行了相当广泛的观测，这些观测清楚地表明：对它们不寻常行为的所有解释都失败了。”
The mystery investigated by the team dates back to the 1930s and affects about a third of Sun-like stars in our Milky Way and other galaxies. All stars with masses similar to our Sun become, towards the end of their lives, red, cool and extremely large, just before retiring as white dwarfs. Also known as red giants, these elderly stars exhibit very strong periodic variations in their luminosity over timescales up to a couple of years.
天文学家对这个谜的调查可以追溯到20世纪30年代，并影响到银河系和其他星系中1/3的类太阳恒星。与我们太阳质量类似的恒星，在其生命晚期变成白矮星之前，都将变成极为巨大而寒冷的红巨星。这些老年恒星表现出非常强的周期性光度变化，一般为1、2年。
“Such variations are thought to be caused by what we call ‘stellar pulsations’,” says Nicholls. “Roughly speaking, the giant star swells and shrinks, becoming brighter and dimmer in a regular pattern. However, one third of these stars show an unexplained additional periodic variation, on even longer timescales — up to five years.”
Nicholls说：“以前这种光度变化被认为由‘恒星脉动’造成，大致上说，恒星有规律的膨胀收缩，光度就（周期性）变亮、变暗。但是，1/3的类太阳恒星显示出一种难以解释的附加的周期性光度变化，其时间甚至长达5年。
In order to find out the origin of this secondary feature, the astronomers monitored 58 stars in our galactic neighbour, the Large Magellanic Cloud, over two and a half years. They acquired spectra using the high resolution FLAMES/GIRAFFE spectrograph on ESO’s Very Large Telescope and combined them with images from other telescopes [1], achieving an impressive collection of the properties of these variable stars.
为了找出这种次要周期的起源，天文学家在我们的邻居——大麦哲伦星系（LMC）中连续监测了58个恒星，时间超过两年半。他们使用甚大望远镜（VLT）上的高分辨率光谱仪——FLAMES/GIRAFFE，并结合了其他天文台的光学图像，完成了这些变星令人难忘的数据收集。
Outstanding sets of data like the one collected by Nicholls and her colleagues often offer guidance on how to solve a cosmic puzzle by narrowing down the plethora of possible explanations proposed by the theoreticians. In this case, however, the observations are incompatible with all the previously conceived models and re-open an issue that has been thoroughly debated. Thanks to this study, astronomers are now aware of their own “ignorance” — a genuine driver of the knowledge-seeking process, as the ancient Greek philosopher Socrates is said to have taught.
Nicholls和她的同事收集的这些杰出的数据集，为我们缩小理论家提供的各种过多的可能性、解决宇宙之谜提供了指导。在本例中，观测结果与已有的模型都不符，并重新引发了一场彻底的辩论。感谢本文的研究，现在天文学家意识到他们很“无知”：一个真正的求知过程，古希腊哲学家苏格拉底曾经这么教导我们的。（苏格拉底的这些我不懂，不过我们都知道知识的三段论——gohomeman1注）
“The newly gathered data show that pulsations are an extremely unlikely explanation for the additional variation,” says team leader Peter Wood. “Another possible mechanism for producing luminosity variations in a star is to have the star itself move in a binary system. However, our observations are strongly incompatible with this hypothesis too.”
研究团队领导Peter Wood说：“新收集的数据证明脉动完全不能解释附加的亮度变化，另一种产生光度变化的可能解释是恒星处于双星系统中。然而，我们的观测与这种解释严重矛盾。”
The team found from further analysis that whatever the cause of these unexplained variations is, it also causes the giant stars to eject mass either in clumps or as an expanding disc. “A Sherlock Holmes is needed to solve this very frustrating mystery,” concludes Nicholls.
团队深入分析后发现，无论造成光变的原因是什么，它总会导致红巨星损失质量，要么形成气体云，要么形成扩展的气体盘。“我们需要一位福尔摩斯侦探来解决这个难题，” Nicholls总结道。

Note   附注
[1] Precise brightness measurements were made by the MACHO and OGLE collaborations, running on telescopes in Australia and Chile, respectively. The OGLE observations were made at the same time as the VLT observations.
1、精确的亮度测量分别由位于智利和澳大利亚天文台的MACHO、OGLE仪实施。OGLE的观测与VLT同步进行。

The FLAMES instrument, mounted at the Nasmyth A platform of Kueyen, UT2 of ESO's Very Large Telescope.FLAMES is the multi-object, intermediate and high resolution spectrograph of the VLT.
上图说明：安装在名为Kueyen（当地土语，“月亮”）的2#甚大望远镜（VLT）内史密斯焦点上的FLAMES仪，它是VLT的多目标、中高分辨率光谱仪。

More Information
更多信息
This research was presented in two papers: one appeared in the November issue of the Monthly Notices of the Royal Astronomical Society (“Long Secondary Periods in Variable Red Giants”, by C. P. Nicholls et al.), and the other has just been published in the Astrophysical Journal (“Evidence for mass ejection associated with long secondary periods in red giants”, by P. R. Wood and C. P. Nicholls).
研究报告已经发表在以下两个刊物上：
2009.11的《皇家天文学会月刊》：“变光红巨星的次级长周期光度变化现象”，作者C. P. Nicholls等；
最新的《天体物理学》期刊：“红巨星抛射物质与其次级长周期光度变化有关的证据”，作者P. R. Wood、C. P. Nicholls。
The team is composed of Christine P. Nicholls and Peter R. Wood (Research School of Astronomy and Astrophysics, Australia National University), Maria-Rosa L. Cioni (Centre for Astrophysics Research, University of Hertfordshire, UK) and Igor Soszyński (Warsaw University Observatory).
研究团队包括：
澳大利亚国立大学，天文和天体物理研究院 Christine P. Nicholls、Peter R. Wood；
英国赫特福德大学，天体物理研究中心 Maria-Rosa L. Cioni；
波兰华沙大学天文台 Igor Soszyński。
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
ESO,欧洲南方天文台的缩写，欧洲最著名的government间合作的天文组织，由14个国家出资组成：澳大利亚、比利时、捷克共和国、丹麦、法国、芬兰、德国、意大利、荷兰、葡萄牙、西班牙、瑞典、瑞士和英国。ESO致力于一项雄心勃勃的计划：设计、建造和操作强大的地面望远镜群，使天文学家观测宇宙、做出重大科学发现。ESO同时在推动、组织天文合作研究中扮演带头人角色。在智利北部阿塔卡马沙漠区域，ESO运作三个独特的、世界级的天文台：拉斯拉、帕拉纳尔和查南托天文台，ESO运作的甚大望远镜（VLT）阵列，是世界上最先进的可见光天文望远镜群。欧洲各伙伴共有的革命性天文台——ESO的ALMA，是当今最大的射电望远镜项目。ESO眼下正计划一个42米口径的欧洲极大可见光/近红外望远镜项目，缩写为E-ELT，将成为全球最大的巡天眼。

The GIRAFFE spectrograph, a major component of the VLT Fibre Large Array Multi-Element Spectrograph (FLAMES) , during the present assembly at the ESO Headquarters in Garching (Germany).
下图说明：GIRAFFE是VLT的大型光纤阵列多目标摄谱仪（FLAMES）的主要部件，图中所示为其在德国加兴市的ESO总部中的安装流程中。

Links
相关链接

• Research       papers: http://arxiv.org/abs/0907.2975 and http://arxiv.org/abs/0910.4418
  本文的2个专业研究报告链接，但我访问不了。

Contacts
作者联系方式
Christine Nicholls and Peter Wood
Mount Stromlo Observatory, Australia
澳大利亚，史创罗峰天文台
Phone: +61-2-6125 0222; +61-2-6125 8032
E-mail:  Nicholls (at) mso.anu.edu.au; wood (at) mso.anu.edu.au

真是一个谜团啊。

欢迎大家就本文内容进行讨论。好了，现在连渐进分支巨星（AGB）的演化都搞不清了。

呵呵，太阳们也有喜怒哀乐

大家能下载那两篇论文吗？如果可以的话，就算我多此一举了。
我下载下来可是每个都大于2M，由于论坛限制，所以只好分卷压缩了。感兴趣的同好，若上面的链接不能下载的话，可以点击本楼的链接。

0907.2975：

0907.2975v1.part1.rar (976.56 KB, 下载次数: 784)

2009-12-13 19:14 上传

点击文件名下载附件

  

0907.2975v1.part2.rar (976.56 KB, 下载次数: 771)

2009-12-13 19:14 上传

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0907.2975v1.part3.rar (691.22 KB, 下载次数: 770)

2009-12-13 19:14 上传

点击文件名下载附件

0910.4418：

0910.4418v1.part1.rar (976.56 KB, 下载次数: 775)

2009-12-13 19:22 上传

点击文件名下载附件

0910.4418v1.part2.rar (976.56 KB, 下载次数: 787)

2009-12-13 19:22 上传

点击文件名下载附件

0910.4418v1.part3.rar (207.92 KB, 下载次数: 1044)

2009-12-13 19:22 上传

点击文件名下载附件

昏倒，ESO改版了，图库都改了位置，重新修改了链接。