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Impacts of stellar evolution and dynamics on the habitable zone: The role of rotation and magnetic activity

机译:恒星演化和动力学对可居住区的影响:旋转和磁活动的作用

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Context. With the ever growing number of detected and confirmed exoplanets, the probability of finding a planet that looks like the Earth increases continuously. While it is clear that the presence of a planet in the habitable zone does not imply the planet is habitable, a systematic study of the evolution of the habitable zone is required to account for its dependence on stellar parameters. Aims. In this article, we aim to provide the community with the dependence of the habitable zone upon the stellar mass, metallicity, rotation, and for various prescriptions of the limits of the habitable zone. Methods. We use stellar evolution models computed with the code STAREVOL, which includes the most current physical mechanisms of internal transport of angular momentum and external wind braking, to study the evolution of the habitable zone and the continuously habitable zone limits. Results. The stellar parameters mass and metallicity affect the habitable zone limits most dramatically. Conversely, for a given stellar mass and metallicity, stellar rotation has only a marginal effect on these limits and does not modify the width of the habitable zone. Moreover, and as expected in the main-sequence phase and for a given stellar mass and metallicity, the habitable zone limits remain almost constant, and this confirms the usual assumptions of a relative constancy of these limits during that phase. The evolution of the habitable zone limits is also correlated to the evolution of the stellar activity (through the Rossby number), which depends on the stellar mass considered. While the magnetic activity has negligible consequence in the case of more massive stars, these effects may have a strong impact on the habitability of a planet around M-dwarf stars. Thus, stellar activity cannot be neglected and may have a strong impact on the development of life during the early stage of the continuously habitable zone phase of low-mass stars. Using observed trends of stellar magnetic field strength, we also constrain the planetary magnetic field (at the zero order) required for a sufficient magnetospheric protection during the whole stellar evolution. Conclusions. We explain for the first time the systematic dependence of planet habitability on stellar parameters along the full evolution of low- and intermediate-mass stars. These results can be used as physical inputs for a first order estimation of exoplanetary habitability.
机译:上下文。随着被探测和确认的系外行星数量的不断增长,找到看起来像地球的行星的可能性不断增加。显然,在宜居区域中存在行星并不意味着该行星是宜居的,但需要对宜居区域的演变进行系统研究,以说明其对恒星参数的依赖性。目的在本文中,我们旨在为社区提供可居住区域对恒星质量,金属性,旋转以及可居住区域界限的各种规定的依赖。方法。我们使用由代码STAREVOL计算的恒星演化模型,其中包括角动量内部传输和外部风制动的最新物理机制,来研究可居住区域和连续可居住区域极限的演变。结果。恒星参数质量和金属性最显着地影响宜居区域的限制。相反,对于给定的恒星质量和金属性,恒星旋转仅对这些限制产生边际影响,而不会改变可居住区域的宽度。而且,正如在主序列阶段中所预期的,并且对于给定的恒星质量和金属性,可居住区域限制几乎保持恒定,这证实了在该阶段这些限制相对恒定的通常假设。可居住区界限的演变也与恒星活动的演变(通过Rossby数)有关,这取决于所考虑的恒星质量。虽然对于较大质量的恒星,磁活动的影响可以忽略不计,但这些影响可能会对M型矮星周围的行星的可居住性产生强烈影响。因此,在低质量恒星连续可居住区阶段的早期阶段,恒星的活动不能被忽略,并且可能对生命的发展产生重大影响。利用观测到的恒星磁场强度趋势,我们还限制了在整个恒星演化过程中足够的磁层保护所需的行星磁场(零级)。结论。我们第一次解释了行星宜居性在低质量和中等质量恒星的完全演化过程中对恒星参数的系统依赖性。这些结果可用作对行星外适居性的一阶估算的物理输入。

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