Nightside condensation of iron in an ultra-hot giant exoplanet
Nightside condensation of iron in an ultra-hot giant exoplanet
复制标题
超热巨型系外行星夜面的铁凝结
DOI：
10.1038/s41586-020-2107-1
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发表时间：
2020
期刊：
影响因子：
64.8
通讯作者：
F. Zerbi
中科院分区：
文献类型：
--
作者：
D. Ehrenreich;C. Lovis;R. Allart;M. Z. Zapatero Osorio;F. Pepe;S. Cristiani;R. Rebolo;N. Santos;F. Borsa;O. Demangeon;X. Dumusque;J. G. González Hernández;N. Casasayas;D. Ségransan;S. Sousa;M. Abreu;V. Adibekyan;M. Affolter;C. Allende Prieto;Y. Alibert;M. Aliverti;D. Alves;M. Amate;G. Ávila;V. Baldini;T. Bandy;W. Benz;A. Bianco;É. Bolmont;F. Bouchy;V. Bourrier;C. Broeg;A. Cabral;G. Calderone;E. Pallé;H. Cegla;R. Cirami;J. Coelho;P. Conconi;I. Coretti;C. Cumani;G. Cupani;H. Dekker;B. Delabre;S. Deiries;V. D’Odorico;P. Di Marcantonio;P. Figueira;A. Fragoso;L. Genolet;M. Genoni;R. Génova Santos;N. Hara;I. Hughes;O. Iwert;F. Kerber;J. Knudstrup;M. Landoni;B. Lavie;J. Lizon;M. Lendl;G. Lo Curto;C. Maire;A. Manescau;C. Martins;D. Megevand;A. Mehner;G. Micela;A. Modigliani;P. Molaro;M. Monteiro;M. Monteiro;M. Moschetti;E. Müller;Nelson Nunes;L. Oggioni;A. Oliveira;G. Pariani;L. Pasquini;E. Poretti;J. L. Rasilla;E. Redaelli;M. Riva;S. Santana Tschudi;P. Santin;P. Santos;Alex Segovia Milla;J. Seidel;D. Sosnowska;A. Sozzetti;P. Spano;A. Suárez Mascareño;H. Tabernero;F. Tenegi;S. Udry;A. Zanutta;F. Zerbi
超热巨型系外行星受到数千倍于地球的日照 1 , 2 。它们的高温大气（超过 2,000 开尔文）是研究极端行星气候和化学的理想实验室 3 – 5 。预计白天将无云，主要由原子种类 6 组成，并且比夜晚更热 5 , 7 , 8 。预计原子会在夜间重新组合成分子 9 ，从而产生不同的白天和夜间化学反应。尽管已观察到金属元素和大的温度对比 10 – 14 ，但尚未在此类系外行星的表面测量到化学梯度。然而，昼夜（“晚上”）和昼夜（“早晨”）终结者之间不同的大气化学性质可能会被揭示为凌日期间的不对称吸收特征 4 , 7 , 15 。在这里，我们报告了在超热系外行星 WASP-76b 中检测到的不对称大气特征。我们结合使用高色散光谱和大光子收集区域，在光谱和时间上解析了这个特征。归因于中性铁的吸收信号在后肢上每秒蓝移 -11 ± 0.7 公里，这可以通过行星自转和从炎热的白天吹来的风的结合来解释 16 。相比之下，靠近早晨明暗界线的夜面没有发出任何信号，这表明原子铁没有吸收那里的星光。我们得出的结论是，铁在穿越夜面的过程中必定会凝结。一颗超热巨型系外行星白天大气中的铁吸收线在穿过夜晚一侧后消失，表明铁在其旅行过程中已经凝结。
Ultrahot giant exoplanets receive thousands of times Earth’s insolation 1 , 2 . Their high-temperature atmospheres (greater than 2,000 kelvin) are ideal laboratories for studying extreme planetary climates and chemistry 3 – 5 . Daysides are predicted to be cloud-free, dominated by atomic species 6 and much hotter than nightsides 5 , 7 , 8 . Atoms are expected to recombine into molecules over the nightside 9 , resulting in different day and night chemistries. Although metallic elements and a large temperature contrast have been observed 10 – 14 , no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night (‘evening’) and night-to-day (‘morning’) terminators could, however, be revealed as an asymmetric absorption signature during transit 4 , 7 , 15 . Here we report the detection of an asymmetric atmospheric signature in the ultrahot exoplanet WASP-76b. We spectrally and temporally resolve this signature using a combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by −11 ± 0.7 kilometres per second on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside 16 . In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. We conclude that iron must therefore condense during its journey across the nightside. Absorption lines of iron in the dayside atmosphere of an ultrahot giant exoplanet disappear after travelling across the nightside, showing that the iron has condensed during its travel.