Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
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DOI：
10.1051/0004-6361/201834504
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发表时间：
2019-04
影响因子：
6.5
通讯作者：
F. Wunderlich;M. Godolt;J. Grenfell;S. Städt;Alexis M. S. Smith;S. Gebauer;F. Schreier;P. Hedelt-P.-He
中科院分区：
文献类型：
--
作者：
F. Wunderlich;M. Godolt;J. Grenfell;S. Städt;Alexis M. S. Smith;S. Gebauer;F. Schreier;P. Hedelt-P.-He
上下文描述系外行星的大气是未来几十年系外行星科学的主要目标之一。目标。利用未来的詹姆斯·韦伯空间望远镜（JWST）研究了M矮星周围适居带（HZ）类地行星的大气光谱特征的探测能力。方法.我们使用耦合的一维气候化学模型来模拟一系列观测到的和模拟的M-矮星光谱对类地行星的影响。模拟的大气作为输入，使用逐线光谱辐射传输模型计算假想行星的透射光谱。为了研究JWST吸收带的光谱可探测性，我们进一步开发了一个信噪比（S/N）模型，并将其应用于我们的透射光谱。结果与早期的M矮行星相比，中晚期M矮行星周围的类地行星大气中甲烷（CH 4）和水（H2O）的高丰度增加了相应光谱特征的可探测性。中晚期M型矮行星的中层大气温度升高，使大气层扩大，进一步增加了吸收带的可探测性。为了探测一颗围绕M型中晚期矮星的类地行星大气中的CH 4、H2O和二氧化碳（CO2），用JWST观测一次凌日就足够了，最远距离为4 pc，最远距离为10 pc，不到10次凌日。由于JWST的饱和极限和不太明显的吸收带，要探测大多数早期M矮星周围的假想类地行星的光谱特征，需要超过10次凌日。我们确定了276个现有的M矮星（包括GJ 1132，TRAPPIST-1，GJ 1214和LHS 1140），在这些矮星周围，假设的类地行星的大气吸收特征可以通过共同添加几个凌日来检测。结论. TESS卫星可能会在距离地球15 pc的范围内发现新的凌日类地行星。我们表明，使用透射光谱，JWST可以提供足够的精度，能够部分地解释TESS发现的大气层，其组成类似于中晚期M矮星。
Context. The characterisation of the atmosphere of exoplanets is one of the main goals of exoplanet science in the coming decades. Aims. We investigate the detectability of atmospheric spectral features of Earth-like planets in the habitable zone (HZ) around M dwarfs with the future James Webb Space Telescope (JWST). Methods. We used a coupled 1D climate-chemistry-model to simulate the influence of a range of observed and modelled M-dwarf spectra on Earth-like planets. The simulated atmospheres served as input for the calculation of the transmission spectra of the hypothetical planets, using a line-by-line spectral radiative transfer model. To investigate the spectroscopic detectability of absorption bands with JWST we further developed a signal-to-noise ratio (S/N) model and applied it to our transmission spectra. Results. High abundances of methane (CH4) and water (H2O) in the atmosphere of Earth-like planets around mid to late M dwarfs increase the detectability of the corresponding spectral features compared to early M-dwarf planets. Increased temperatures in the middle atmosphere of mid- to late-type M-dwarf planets expand the atmosphere and further increase the detectability of absorption bands. To detect CH4, H2O, and carbon dioxide (CO2) in the atmosphere of an Earth-like planet around a mid to late M dwarf observing only one transit with JWST could be enough up to a distance of 4 pc and less than ten transits up to a distance of 10 pc. As a consequence of saturation limits of JWST and less pronounced absorption bands, the detection of spectral features of hypothetical Earth-like planets around most early M dwarfs would require more than ten transits. We identify 276 existing M dwarfs (including GJ 1132, TRAPPIST-1, GJ 1214, and LHS 1140) around which atmospheric absorption features of hypothetical Earth-like planets could be detected by co-adding just a few transits. Conclusions. The TESS satellite will likely find new transiting terrestrial planets within 15 pc from the Earth. We show that using transmission spectroscopy, JWST could provide enough precision to be able to partly characterise the atmosphere of TESS findings with an Earth-like composition around mid to late M dwarfs.