近日，美国亚利桑那州立大学的Luis Welbanks及其研究团队取得一项新进展。经过不懈努力，他们揭示一个温暖海王星系外行星的高内部热流和大核心。相关研究成果已于2024年5月20日在国际权威学术期刊《自然》上发表。

在这项工作中，研究人员利用HST WFC3、JWST NIRCam和MIRI的组合，展示了大约750 K、低密度、海王星大小的系外行星WASP-107b的全色透射光谱。从该光谱中，研究人员检测了H₂O (21σ)、CH₄ (5σ)、CO (7σ)、CO₂ (29σ)、SO₂ (9σ)和NH₃ (6σ)的光谱特征。这些分子的存在限制了大气中金属的富集(M/H为10-18× Solar³)、垂直混合强度(log₁₀K_zz= 8.4-9.0 cm²s^-1)和内部温度(>345 K)。高内部温度暗示了潮汐驱动的暴涨作用于类似海王星的内部结构，这可以合理解释WASP-107b的大半径和低密度。

这些发现表明，偏心驱动的潮汐加热是影响大气化学和内部结构推断的关键因素，对于大多数低温（<1000K）的超级地球到土星质量的系外行星来说都具有重要意义。

据悉，长期以来，系外行星大气与内部性质之间的相互作用一直被假设为气体行星膨胀机制和明显大气化学不平衡条件的驱动因素。然而，由于HST波长覆盖范围的局限性和主要基于单分子（特别是H₂O）的推断，系外行星的透射光谱在验证这些理论方面的能力受到了限制。

附：英文原文

Title: A high internal heat flux and large core in a warm neptune exoplanet

Author: Welbanks, Luis, Bell, Taylor J., Beatty, Thomas G., Line, Michael R., Ohno, Kazumasa, Fortney, Jonathan J., Schlawin, Everett, Greene, Thomas P., Rauscher, Emily, McGill, Peter, Murphy, Matthew, Parmentier, Vivien, Tang, Yao, Edelman, Isaac, Mukherjee, Sagnick, Wiser, Lindsey S., Lagage, Pierre-Olivier, Dyrek, Achrne, Arnold, Kenneth E.

Issue&Volume: 2024-05-20

Abstract: Interactions between exoplanetary atmospheres and internal properties have long been hypothesized to be drivers of the inflation mechanisms of gaseous planets and apparent atmospheric chemical disequilibrium conditions. However, transmission spectra of exoplanets has been limited in its ability to observational confirm these theories due to the limited wavelength coverage of HST and inferences of single molecules, mostly H₂O . In this work, we present the panchromatic transmission spectrum of the approximately 750 K, low-density, Neptune-sized exoplanet WASP-107b using a combination of HST WFC3, JWST NIRCam and MIRI. From this spectrum, we detect spectroscopic features due to H₂O (21σ), CH₄ (5σ), CO (7σ), CO₂ (29σ), SO₂ (9σ), and NH₃ (6σ). The presence of these molecules enable constraints on the atmospheric metal enrichment (M/H is 10–18× Solar³), vertical mixing strength (log₁₀K_zz=8.4–9.0 cm²s^-1), and internal temperature (>345 K). The high internal temperature is suggestive of tidally-driven inflation acting upon a Neptunelike internal structure, which can naturally explain the planet’s large radius and low density. These findings suggest that eccentricity driven tidal heating is a critical process governing atmospheric chemistry and interior structure inferences for a majority of the cool (<1,000K) super-Earth-to-Saturn mass exoplanet population.

DOI: 10.1038/s41586-024-07514-w

Source: https://www.nature.com/articles/s41586-024-07514-w