近日，美国自然历史博物馆的Jacqueline K. Faherty及其研究团队取得一项新进展。经过不懈努力，他们观测到一颗低温褐矮星发射出的甲烷。相关研究成果已于2024年4月17日在国际权威学术期刊《自然》上发表。

本文报道了詹姆斯·韦伯太空望远镜观测到W1935在3.326μm波段强烈的甲烷发射。研究人员通过大气模拟分析，得出结论：这一特征是由以1-10mbar为中心、温度约为300K的逆温层引起的。这一发现代表了在没有主星辐射的情况下，类木星大气中的大气逆温过程。逆温层的强烈现象很可能是由于极光过程加热所致，尽管不能排除其他内部和外部动力过程的可能性。

在进一步的分析中，最符合观测数据的模型排除了H³⁺发射的贡献，这一特征在太阳系的气态巨行星中尤为显著。然而，这与H³⁺在W1935发射源较高压力环境下会迅速破坏的理论是一致的。

据悉，在太阳系之外，科学家们还通过对孤立的褐矮星进行射电观测，推断出太阳系外也存在极光现象。在太阳系中，巨大的行星在电磁波谱上展现出极光发射的特征，如H3+和甲烷的红外发射。然而，在寻找具有极光特征的孤立褐矮星时，尽管人们努力在射电波段寻找相应的红外特征，但迄今为止尚未有探测结果报道。CWISEP j193518.59 - 154620.3.(简称W1935)是一颗孤立的褐矮星，温度约为482K。

附：英文原文

Title: Methane emission from a cool brown dwarf

Author: Faherty, Jacqueline K., Burningham, Ben, Gagn, Jonathan, Surez, Genaro, Vos, Johanna M., Alejandro Merchan, Sherelyn, Morley, Caroline V., Rowland, Melanie, Lacy, Brianna, Kiman, Rocio, Caselden, Dan, Kirkpatrick, J. Davy, Meisner, Aaron, Schneider, Adam C., Kuchner, Marc Jason, Bardalez Gagliuffi, Daniella Carolina, Beichman, Charles, Eisenhardt, Peter, Gelino, Christopher R., Gharib-Nezhad, Ehsan, Gonzales, Eileen, Marocco, Federico, Rothermich, Austin James, Whiteford, Niall

Issue&Volume: 2024-04-17

Abstract: Beyond our Solar System, aurorae have been inferred from radio observations of isolated brown dwarfs. Within our Solar System, giant planets have auroral emission with signatures across the electromagnetic spectrum including infrared emission of H₃⁺ and methane. Isolated brown dwarfs with auroral signatures in the radio have been searched for corresponding infrared features, but only null detections have been reported. CWISEP J193518.59-154620.3. (W1935 for short) is an isolated brown dwarf with a temperature of approximately 482K. Here we report James Webb Space Telescope observations of strong methane emission from W1935 at 3.326μm. Atmospheric modelling leads us to conclude that a temperature inversion of approximately 300K centred at 1–10mbar replicates the feature. This represents an atmospheric temperature inversion for a Jupiter-like atmosphere without irradiation from a host star. A plausible explanation for the strong inversion is heating by auroral processes, although other internal and external dynamical processes cannot be ruled out. The best-fitting model rules out the contribution of H₃⁺ emission, which is prominent in Solar System gas giants. However, this is consistent with rapid destruction of H₃⁺ at the higher pressure where the W1935 emission originates.

DOI: 10.1038/s41586-024-07190-w

Source: https://www.nature.com/articles/s41586-024-07190-w