论文标题

热土星JWST ERO目标WASP-96B上形成云

Clouds form on the hot Saturn JWST ERO target WASP-96b

论文作者

Samra, Dominic, Helling, Christiane, Chubb, Katy, Min, Michiel, Carone, Ludmila, Schneider, Aaron

论文摘要

WASP-96B是一种热土星系外行星,在热力学预期的广泛云形成的状态下,平衡温度很好。先前对Hubble/WFC3,Spitzer/IRAC和VLT/FORS2进行的观察已合并为单个光谱,检索表明该光谱表明冷淡但无云的气氛。最近,在詹姆斯·韦伯(James Webb)太空望远镜(JWST)中观察到了地球,这是早期发行观测(ERO)的一部分。从3D GCM专家/MITGCM的结果中提取1D轮廓,并用作动力学,非平衡模型的输入,以研究混合组成的矿物云颗粒的形成。 Arcis检索框架应用于JWST WASP-96B过境光谱,以研究云模型与假定无云的过境光谱之间的明显矛盾。在黄蜂96b的整个大气中,云被预计无处不在。因此,在影响光谱的低压方案中,硅酸盐材料贡献了40%至90%,因此金属氧化物的贡献高达40%。我们探索如何将这些多云模型与当前可用的大气过境光谱匹配。减少的垂直混合作用可将云沉淀到大气中的深处,而云颗粒的孔隙率增加可降低近红外和光学区域中云的不透明度。这两种效果都可以观察到更清晰的分子特征,同时仍允许云在大气中。黄蜂96b的气氛不太可能无云。 HST,Spitzer和VLT光谱的检索也表明,多个云解决方案会重现数据。 JWST的观察将受云的影响,即使在Niriss波长范围内,云顶压力也会因数量级而变化。 NIRSPEC的长波长端和Miri的短端可能会探测WASP-96B终结器肢体之间的大气不对称。

WASP-96b is a hot Saturn exoplanet, with an equilibrium temperature well within the regime of thermodynamically expected extensive cloud formation. Prior observations with Hubble/WFC3, Spitzer/IRAC, and VLT/FORS2 have been combined into a single spectra for which retrievals suggest a cold but cloud-free atmosphere. Recently, the planet was observed with the James Webb Space Telescope (JWST) as part of the Early Release Observations (ERO). 1D profiles are extracted from the 3D GCM expeRT/MITgcm results and used as input for a kinetic, non-equilibrium model to study the formation of mineral cloud particles of mixed composition. The ARCiS retrieval framework is applied to the pre-JWST WASP-96b transit spectra to investigate the apparent contradiction between cloudy models and assumed cloud-free transit spectra. Clouds are predicted to be ubiquitous throughout the atmosphere of WASP-96b. Silicate materials contribute between 40% and 90%, hence, also metal oxides contribute with up to 40% in the low-pressure regimes that effect the spectra. We explore how to match these cloudy models with currently available atmospheric transit spectra. A reduced vertical mixing acts to settle clouds to deeper in the atmosphere, and an increased cloud particles porosity reduces the opacity of clouds in the near-IR and optical region. Both these effects allow for clearer molecular features to be observed, while still allowing clouds to be in the atmosphere. The atmosphere of WASP-96b is unlikely to be cloud free. Also retrievals of HST, Spitzer and VLT spectra show that multiple cloudy solutions reproduce the data. JWST observations will be affected by clouds, where within even the NIRISS wavelength range the cloud top pressure varies by an order of magnitude. The long wavelength end of NIRSpec and short end of MIRI may probe atmospheric asymmetries between the limbs of the terminator on WASP-96b.

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