Near and Far: White Dwarfs, Brown Dwarfs and a New Standard Candle

远近：白矮星、褐矮星和新标准蜡烛

• 批准号: RGPIN-2022-03051
• 负责人: Richer, Harvey
• 金额: $ 3.64万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=763075
• 关键词: Near; Far; White; Dwarfs; Brown

The research of the scientific program funded by this grant will take us from stars in the neighbourhood of the Sun to the furthest reaches of the universe. It will exploit the most sophisticated modern telescopes currently available to the world community, justifying Canada's contributions to these frontline facilities. It will expose HQP to a high impact international collaboration and provide a unique science experience that spans all of space and time.  The nearby region: (a) The fact that we can see stars means they are losing energy and hence evolving. For almost all stars, this energy is produced by nuclear reactions in the hot dense stellar core which consumes the star's hydrogen and produces heavier elements. At the end of this nuclear processing the star ejects all the material above its nuclear burning region, exposing the extremely dense and hot core which then slowly cools with time. The resulting stellar object is called a white dwarf (WD); typically half the mass of the Sun with a radius roughly that of the Earth. The most massive star capable of forming a WD is an extremely important quantity, all stars more massive than this limit explode as supernovae (SN) which control the chemical evolution and star formation rate in a galaxy. To determine this upper mass limit we have been exploring young star clusters that contain massive stars up to 10 or more times the mass of the Sun and establishing which of them produced WDs. It has been extremely challenging to locate WDs whose progenitor was more than 6 times the mass of the Sun, but some new ideas and techniques we have been developing is showing promise.   (b) We were successful in obtaining 20.5 hours of time on the soon-to-be-launched James Webb Space Telescope to search for (among other things) possible evidence of planetary systems around very old stars. The search will be in an ancient star cluster, imaging its WDs in the infrared (IR). About 5% of young WDs in the galaxy are known to be anomalously bright in the IR due to dust resulting from the destruction of planets or asteroids when the host star transitioned to a WD. Our search will be amongst the 12 billion year WDs in this ancient stellar system looking for evidence of planet formation in the very early universe. The distant region: The Hubble Constant, measuring the expansion rate of the universe, is one of the most fundamental cosmological parameters. Currently, the value from the standard cosmological model is in conflict with measurements in the local universe. Suggested causes range from systematic biases in one or both techniques to underestimated uncertainties in distance calibration, to the possibility of new physics in the early universe. To explore this conflict further we have developed a new distance technique using very luminous carbon-rich red giant stars. While still in its infancy, the method is proving to be extremely powerful and requires significantly less observing time than the standard techniques.

这笔赠款资助的科学计划的研究将使我们从太阳附近的恒星到宇宙最远的范围。它将探索当前可用于世界社区的最复杂的现代望远镜，证明加拿大对这些一线设施的贡献是合理的。它将暴露于HQP进行高影响力的国际合作，并提供独特的科学经验，并跨越所有时空。附近的地区：（a）我们可以看到恒星的事实意味着它们正在失去能量并因此不断发展。对于几乎所有恒星，这种能量是由热致密恒星芯中的核反应产生的，该核心消耗了恒星的氢并产生较重的元素。在此核处理结束时，恒星估计了其核燃烧区域上方的所有材料，暴露了极度致密和热的核心，然后随着时间的流逝而慢慢冷却。结果恒星对象称为白矮人（WD）；通常，阳光的一半质量大约是地球的半径。能够形成WD的最庞大的恒星是极其重要的数量，所有恒星都比该极限探索更大的恒星，因为它控制着银河系中的化学演化和恒星形成速率。为了确定这种上限限制，我们已经探索了年轻的恒星簇，这些星团包含巨大的恒星，最多是太阳质量的10倍或更多倍，并确定其中哪个产生了WD。找到祖先的WD是太阳质量的6倍以上，但我们一直在开发的一些新想法和技术表现出希望是非常挑战。 （b）我们成功地在即将发布的詹姆斯·韦伯太空望远镜上获得了20.5个小时的时间，以搜索（除其他）可能的旧恒星周围行星系统的可能证据。搜索将在一个古老的恒星集群中，将其在红外线（IR）中成像。由于宿主恒星过渡到WD时，由于尘埃破坏了行星或小行星，因此已知银河系中约5％的年轻WD在IR中是异常明亮的。我们的搜索将是这个古老的恒星体系中的120亿年WD，以寻找早期宇宙中行星形成的证据。拆卸区域：测量宇宙膨胀速率的哈勃常数是最基本的宇宙学参数之一。当前，标准宇宙学模型的价值与当地宇宙中的测量值冲突。建议的原因范围从一种或两种技术的系统偏见到低估距离校准的不确定性到早期宇宙中新物理的可能性。为了进一步探索这一冲突，我们使用非常发光的碳红色巨星开发了一种新的距离技术。尽管仍处于起步阶段，但该方法被证明非常强大，并且比标准技术所需的观察时间要少得多。