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把我们从太阳附近的恒星带到宇宙最远的地方，它将利用国际社会目前可用的最先进的现代望远镜，证明加拿大对这些前沿的贡献是合理的。它将让 HQP 参与具有高影响力的国际合作，并提供跨越所有空间和时间的独特科学体验：​（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演化。对于几乎所有的人来说。对于恒星来说，这种能量是由热致密恒星核心中的核反应产生的，该核反应消耗恒星的氢并产生较重的元素。在核处理结束时，恒星喷射出其核燃烧区域上方的所有物质，暴露出极其致密和炽热的物质。然后随着时间的推移慢慢冷却的恒星物体被称为白矮星（WD）；质量通常是太阳的一半，半径与地球大致相同，能够形成白矮星的质量最大的恒星是极其重要的。数量，所有恒星都比这个质量大为了确定这个质量上限，我们一直在探索包含质量高达太阳质量 10 倍或更多的恒星的年轻星团，并建立了超新星 (SN) 控制星系中化学演化和恒星形成速率的极限爆炸。定位 WD 的来源是太阳质量的 6 倍以上，但我们一直在开发的一些新想法和技术显示出希望 (b) 我们成功地获得了 20.5。即将发射的詹姆斯·韦伯太空望远镜将花费数小时来寻找（除其他外）非常古老恒星周围行星系统的可能证据。搜索将在一个古老的星团中进行，在红外中对其进行WD成像。 （红外）已知，银河系中大约 5% 的年轻白星在红外区域异常明亮，这是由于我们的搜索将导致行星或小行星毁灭时产生的尘埃。在这个古老的恒星系统中进行 120 亿年的观测，寻找极早期宇宙中行星形成的证据：哈勃常数，测量宇宙的膨胀率，是目前最基本的宇宙学参数之一。 ，标准宇宙学模型的值与局部宇宙的测量相冲突，所提出的原因包括一种或两种技术的系统偏差、距离校准的不确定性被低估，以及早期宇宙中新物理学的可能性。冲突此外，我们还开发了一种使用非常明亮的富碳红巨星的新距离技术，尽管该方法仍处于起步阶段，但事实证明该方法非常强大，并且比标准技术所需的观测时间要少得多。