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arXiv 1503.04189astro-ph.EP
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鲸鱼座τ的化学组成及其对类地行星的可能影响

The Chemical Composition of τ Ceti and Possible Effects on Terrestrial Planets

Michael Pagano, Amanda Truitt, Patrick A. Young, Sang-Heon Shim

摘要:

鲸鱼座τ(HD 10700)是一颗G8矮星,太阳质量为0.78,是一颗近距离(3.65 pc)的类太阳恒星,最近发现了5颗可能的类地行星候选者(最小质量为2、3.1、3.5、4.3和6.7地球质量)。我们使用麦哲伦号上的MIKE摄谱仪的光谱报告了23种元素的丰度。利用这里确定的丰度的恒星模型,我们计算了经典的宜居带随时间的位置。在目前最适合的年龄,7.63戈瑞,多达两个行星(e和f)可能在宜居带,这取决于大气性质。该恒星的Mg/Si比为1.78,远高于地球(约1.2)。在这样一个镁与硅的比例过剩的系统中,鲸鱼座τ周围行星的矿物组成可能与地球有很大的不同,可能是MgO过饱和,导致橄榄石和铁方镁石的含量比地球增加。MgO的增加将对鲸鱼座τ周围行星的地幔流变学产生巨大的影响。

英文摘要:

τ Ceti (HD10700), a G8 dwarf with solar mass of 0.78, is a close (3.65 pc) sun-like star where 5 possibly terrestrial planet candidates (minimum masses of 2, 3.1, 3.5, 4.3, and 6.7 Earth masses) have recently been discovered. We report abundances of 23 elements using spectra from the MIKE spectrograph on Magellan. Using stellar models with the abundances determined here, we calculate the position of the classical habitable zone with time. At the current best fit age, 7.63 Gy, up to two planets (e and f) may be in the habitable zone, depending on atmospheric properties. The Mg/Si ratio of the star is found to be 1.78, which is much greater than for Earth (about 1.2). With a system that has such an excess of Mg to Si ratio it is possible that the mineralogical make-up of planets around τ Ceti could be significantly different from that of Earth, with possible oversaturation of MgO, resulting in an increase in the content of olivine and ferropericlase compared with Earth. The increase in MgO would have a drastic impact on the rheology of the mantles of the planets around τ Ceti.

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