Understanding Stellar Variability and Improving Exoplanet Characterisation

了解恒星变率并改善系外行星特征

基本信息

  • 批准号:
    2590540
  • 负责人:
  • 金额:
    --
  • 依托单位:
  • 依托单位国家:
    英国
  • 项目类别:
    Studentship
  • 财政年份:
    2021
  • 资助国家:
    英国
  • 起止时间:
    2021 至 无数据
  • 项目状态:
    未结题

项目摘要

Almost everything we know about exoplanets, those planets outside of our solar system, is derived from the stars they orbit. This is because, like our Sun relative to the Earth, the host stars vastly outshine any companion planets. As a result, inhomogeneities and variability on the surface of the host stars can significantly impair the ability to detect and characterise exoplanets; this is especially true for temperate, rocky planets as their signals are inherently small. The first exoplanet around a Sun-like star was discovered through the radial velocity technique (Mayor & Queloz 1995), i.e. measuring the Doppler reflex motion induced in the host star by the planet as they orbit about their common centre of mass. Since this discovery we have come a long ways, detecting thousands of exoplanets and significantly improving the precision of our instruments. However, we are yet to find a true analogue to our Earth, the only known planet to support life. Thanks to instruments like the ESPRESSO spectrograph on the VLT, we now are within the technological capabilities to detect rocky, temperate planets around Sun-like stars, yet this remains an enormous challenge. Perhaps the biggest stumbling block on the pathway to habitable alien worlds originates from the host stars themselves.Inhomogeneities on the surfaces of the exoplanet host stars can produce spurious radial velocity signals that may mask or even mimic the Doppler wobble of an exoplanet. This happens both because the plasma on the stellar surface is moving, and thus emitting its own Doppler shifts, but also because magnetic field concentrations can suppress these motions and alter brightness of the surface in these regions. Moreover, the variability originating from the surface of the Sun (and Sun-like stars) is orders of magnitude larger than the ~9 cm/s Doppler wobble induced by the Earth. This project focuses on improving our knowledge of stellar physics so that we may disentangle stellar and planetary signals to enable the future confirmation and characterisation of rocky, temperate worlds around Sun-like stars. Almost all stellar variability is driven by the interplay between convection and magnetic fields; hence, understanding this interplay is key to unveiling low-mass, long-period planets. On the surface of our Sun, hot bubble of gas (known as granules) rise to the surface, cool, and fall back down into the star (within intergranular lanes); the uprising motions give rise to Doppler shifts towards the bluer end of the spectrum, while the falling motions shift the light towards the redder end of the spectrum. This introduces asymmetries into the stellar absorptions lines used to measure Doppler shifts, as well as net shifts of several 10s of cm/s to a several m/s, depending the interplay with the magnetic field. This project will use state-of-the-art 3D magnetohydrodynamical (MHD) simulations to create the most realistic stellar simulations to date. Creating a suite of stellar models will allow us to study how the convection is altered at various magnetic field strengths and how this imprints itself in a number of different (typical) stellar absorption lines. The goal is to develop a toolkit to identify and mitigate stellar variability in exoplanet data, thereby pushing our detections levels even further and helping to open a pathway to the confirmation and characterisation of Earth-like alien worlds.
我们对系外行星(即太阳系外的行星)的了解,几乎都来自于它们所围绕的恒星。这是因为,就像我们的太阳相对于地球一样,主星比任何伴星都要亮得多。因此,宿主恒星表面的不均匀性和可变性会严重损害探测和表征系外行星的能力;对于温带的岩石行星来说尤其如此,因为它们的信号本来就很小。第一颗围绕类太阳恒星运行的系外行星是通过径向速度技术(Mayor & Queloz 1995)发现的,即测量行星在围绕其共同质心运行时在主星中引起的多普勒反射运动。自从这一发现以来,我们已经取得了长足的进步,探测了数千颗系外行星,并显著提高了仪器的精度。然而,我们还没有找到一个真正类似于地球的行星,地球是唯一已知的支持生命的行星。由于VLT上的ESPRESSO光谱仪等仪器,我们现在有了探测类太阳恒星周围的岩石、温带行星的技术能力,但这仍然是一个巨大的挑战。也许通往宜居外星世界的最大障碍来自宿主恒星本身。系外行星宿主恒星表面的不均匀性可能产生虚假的径向速度信号,这些信号可能掩盖甚至模仿系外行星的多普勒摆动。这不仅是因为恒星表面的等离子体在运动,从而释放出自己的多普勒频移,还因为磁场的集中可以抑制这些运动,改变这些区域表面的亮度。此外,来自太阳(和类太阳恒星)表面的变化比地球引起的~9厘米/秒的多普勒摆动要大几个数量级。这个项目的重点是提高我们对恒星物理学的认识,这样我们就可以解开恒星和行星的信号,以便将来确认和描述类太阳恒星周围的岩石、温带世界。几乎所有的恒星变化都是由对流和磁场之间的相互作用驱动的;因此,了解这种相互作用是揭示低质量、长周期行星的关键。在我们的太阳表面,热气泡(被称为颗粒)上升到表面,冷却,并回落到恒星(在粒间带);上升运动使光向光谱的较蓝端移动,而下降运动使光向光谱的较红端移动。这就引入了用于测量多普勒频移的恒星吸收线的不对称性,以及根据与磁场的相互作用,从几厘米/秒到几米/秒的净频移。该项目将使用最先进的3D磁流体动力学(MHD)模拟来创建迄今为止最逼真的恒星模拟。创建一套恒星模型将使我们能够研究对流在不同磁场强度下是如何改变的,以及这是如何在许多不同(典型)的恒星吸收线上留下印记的。目标是开发一个工具包来识别和减轻系外行星数据中的恒星变异性,从而进一步推动我们的探测水平,并帮助开辟一条确认和描述类地外星世界的途径。

项目成果

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其他文献

吉治仁志 他: "トランスジェニックマウスによるTIMP-1の線維化促進機序"最新医学. 55. 1781-1787 (2000)
Hitoshi Yoshiji 等:“转基因小鼠中 TIMP-1 的促纤维化机制”现代医学 55. 1781-1787 (2000)。
  • DOI:
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    0
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LiDAR Implementations for Autonomous Vehicle Applications
  • DOI:
  • 发表时间:
    2021
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  • 影响因子:
    0
  • 作者:
  • 通讯作者:
生命分子工学・海洋生命工学研究室
生物分子工程/海洋生物技术实验室
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吉治仁志 他: "イラスト医学&サイエンスシリーズ血管の分子医学"羊土社(渋谷正史編). 125 (2000)
Hitoshi Yoshiji 等人:“血管医学与科学系列分子医学图解”Yodosha(涉谷正志编辑)125(2000)。
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Effect of manidipine hydrochloride,a calcium antagonist,on isoproterenol-induced left ventricular hypertrophy: "Yoshiyama,M.,Takeuchi,K.,Kim,S.,Hanatani,A.,Omura,T.,Toda,I.,Akioka,K.,Teragaki,M.,Iwao,H.and Yoshikawa,J." Jpn Circ J. 62(1). 47-52 (1998)
钙拮抗剂盐酸马尼地平对异丙肾上腺素引起的左心室肥厚的影响:“Yoshiyama,M.,Takeuchi,K.,Kim,S.,Hanatani,A.,Omura,T.,Toda,I.,Akioka,
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Field Assisted Sintering of Nuclear Fuel Simulants
核燃料模拟物的现场辅助烧结
  • 批准号:
    2908917
  • 财政年份:
    2027
  • 资助金额:
    --
  • 项目类别:
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评估用于航空航天应用的新型抗疲劳钛合金
  • 批准号:
    2879438
  • 财政年份:
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  • 项目类别:
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