论文标题
在超热巨型系外行星中铁的夜边凝结
Nightside condensation of iron in an ultra-hot giant exoplanet
论文作者
论文摘要
超热的巨型系外行星接收了数千倍地球的死亡。它们的高温气氛（> 2,000 K）是研究极端行星气候和化学的理想实验室。预计Dayside是无云的，由原子种类主导，并且比夜间更热。原子有望在夜间重新组合分子中，从而导致不同的昼夜化学。尽管已经观察到金属元素和较大的温度对比度，但在这种系外行星的表面上尚未测量化学梯度。但是，可以在过境期间显示为不对称的吸收签名，在日夜（“晚上”）和夜间（“早上”）终止者之间进行不同的大气化学反应。在这里，我们报告了在超热系外行星WASP-76B中检测到不对称大气签名的检测。由于高分散光谱与较大的光子收集区域的结合，我们在光谱和时间上可以解决此特征。归因于中性铁的吸收信号在尾肢上被-11 +/- 0.7 km S-1蓝光，可以通过炎热的日子里的行星旋转和风吹吹来的结合来解释。相比之下，没有信号来自靠近早晨终结者的夜间，表明原子铁并没有吸收在那里的星光。因此，铁必须在整个夜间旅行中凝结。
Ultra-hot giant exoplanets receive thousands of times Earth's insolation. Their high-temperature atmospheres (>2,000 K) are ideal laboratories for studying extreme planetary climates and chemistry. Daysides are predicted to be cloud-free, dominated by atomic species and substantially hotter than nightsides. Atoms are expected to recombine into molecules over the nightside, resulting in different day-night chemistry. While metallic elements and a large temperature contrast have been observed, 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. Here, we report the detection of an asymmetric atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and temporally resolve this signature thanks to the combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by -11+/-0.7 km s-1 on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. Iron must thus condense during its journey across the nightside.
