Unveiling the ice and gas nature of active centaur (2060) Chiron using the James Webb Space Telescope

IF 5.4 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
N. Pinilla-Alonso, J. Licandro, R. Brunetto, E. Henault, C. Schambeau, A. Guilbert-Lepoutre, J. Stansberry, I. Wong, J. I. Lunine, B. J. Holler, J. Emery, S. Protopapa, J. Cook, H. B. Hammel, G. L. Villanueva, S. N. Milam, D. Cruikshank, A. C. de Souza-Feliciano
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引用次数: 0

Abstract

Context. (2060) Chiron is a large centaur that has been reported active on multiple occasions at relatively large heliocentric distances, including during aphelion passage. Studies of Chiron’s coma during active periods have resulted in the detection of C≡N and CO outgassing. Additionally, Chiron is surrounded by a disk of debris that varies with time. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected.Aims. This work reports the study of the ices on Chiron’s surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs.Methods. In July 2023, the James Webb Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 μm with a resolving power of ∼1000, and compare them with laboratory data for identification of the spectral bands.Results We report the first detections on Chiron of absorption bands of several volatile ices, including CO2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 μm. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 μm.
利用詹姆斯韦伯太空望远镜揭开活跃的半人马座(2060)凯龙星的冰和气体性质
上下文。(2060)凯龙星是一颗大型半人马星,据报道,它在相对较大的日心距离上多次活跃,包括远日点通过期间。对凯龙星在活跃期的昏迷的研究已经发现了C≡N和CO的放出。此外,凯龙星周围环绕着一个随时间变化的碎片盘。要了解凯龙星及其所检测到的气相母分子的活化机制,还需要进行大量的工作。这项工作报告了对凯龙星表面冰和彗发的研究,并寻求与活动相关的挥发物的光谱指标。此外,我们还讨论了这些检测如何与凯龙星和其他半人马星的激活机制相关。2023年7月,詹姆斯·韦伯太空望远镜(JWST)观测到凯龙星在远日点附近活动。我们给出了JWST/NIRSpec光谱范围为0.97 ~ 5.27 μm,分辨率为~ 1000,并将其与实验室数据进行了比较,用于光谱波段的识别。结果首次在Chiron上检测到CO2、CO、C2H6、C3H8、C2H2等几种挥发性冰的吸收带。我们还证实了水冰以无定形存在。从这些数据中产生的一个关键发现是检测到CH4的荧光发射,揭示了富含这种高挥发性分子的气体昏迷的存在,我们也确定它处于非局部热平衡(非lte)。在4.27 μm的基本拉伸带也检测到CO2气体排放。我们认为CH4排放的存在是第一个证明甲烷的解吸由于密度的非晶态低温水冰相变与凯龙星在詹姆斯韦伯太空望远镜观测的估计温度(61 K),检测CH4和CO2光解和质子辐照产品的表面上,在昏迷冰颗粒,或环材料还发现通过森林吸收的特性从3.5到5.3μm。
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来源期刊
Astronomy & Astrophysics
Astronomy & Astrophysics 地学天文-天文与天体物理
CiteScore
10.20
自引率
27.70%
发文量
2105
审稿时长
1-2 weeks
期刊介绍: Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.
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