A ground-based near-infrared emission spectrum of the exoplanet HD 189733b
A ground-based near-infrared emission spectrum of the exoplanet HD 189733b
复制标题
系外行星 HD 189733b 的地面近红外发射光谱
DOI：
10.1038/nature08775
复制
发表时间：
2010
期刊：
影响因子：
64.8
通讯作者：
T. Henning
中科院分区：
文献类型：
--
作者：
M. Swain;P. Deroo;C. Griffith;G. Tinetti;A. Thatte;G. Vasisht;Pin Chen;J. Bouwman;I. Crossfield;D. Angerhausen;C. Afonso;T. Henning
使用红外光谱探测分子探测系外行星大气的条件和组成。水（H2O），甲烷（CH 4），二氧化碳（CO2），和一氧化碳（CO）已被检测到在两个热蒸馏器。这些先前的结果依赖于不提供2.4-5.2 μm光谱区域光谱能力的天基望远镜。在这里，我们报告了HD 189733 b在2.0-2.4 μm和3.1-4.1 μm之间的昼侧发射光谱的地面观测，我们发现了明亮的发射特征。在与天基仪器重叠的地方，我们的结果与以前的测量结果非常一致。在3.25 μm处的特征是意想不到的，并且难以用假设局部热力学平衡（LTE）条件的模型来解释，这些模型通常在1 bar到1 × 10-6 bar的压力下通过红外测量进行采样。对这一特征最可能的解释是，它来自CH 4的非LTE排放，类似于我们太阳系行星大气中所看到的。这些结果表明，在解释强辐射系外行星的测量结果时，可能需要考虑非LTE效应。
Detection of molecules using infrared spectroscopy probes the conditions and compositions of exoplanet atmospheres. Water (H2O), methane (CH4), carbon dioxide (CO2), and carbon monoxide (CO) have been detected in two hot Jupiters. These previous results relied on space-based telescopes that do not provide spectroscopic capability in the 2.4–5.2 μm spectral region. Here we report ground-based observations of the dayside emission spectrum for HD 189733b between 2.0–2.4 μm and 3.1–4.1 μm, where we find a bright emission feature. Where overlap with space-based instruments exists, our results are in excellent agreement with previous measurements. A feature at ∼3.25 μm is unexpected and difficult to explain with models that assume local thermodynamic equilibrium (LTE) conditions at the 1 bar to 1 × 10-6 bar pressures typically sampled by infrared measurements. The most likely explanation for this feature is that it arises from non-LTE emission from CH4, similar to what is seen in the atmospheres of planets in our own Solar System. These results suggest that non-LTE effects may need to be considered when interpreting measurements of strongly irradiated exoplanets.